Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?
Thanks,
Eric

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?
Thanks,
Eric

It sounds goods. Most 2-strokes don't care if they run forward or
backward, as long as the ignition timing is adjusted.

If you showed us your engine, I didn't see it. One exception about
running backwards is if the engine has a rotary intake valve mounted
on the crankshaft. That's been used on some old off-road motorcycle
engines and some other high-performance types, but it's very unlikely
on most other applications. I'm guessing your engine doesn't have
pump/squirt lubrication, which is another limitation on running
backwards.

Lots of 2-strokes run upside-down. As you say, it's a matter of
whether the carb has a float bowl and which way it thinks is "up."

--
Ed Huntress

On Wed, 21 Oct 2015 14:01:25 -0700, etpm wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a 2
stroke bicycle engine upside down. Maybe upside down and backward. If I
did this the carb would need to be inverted because it is a float bowl
type carb. I suppose I could use a pumper type carb instead but I don't
know if I have one that is suitable as far as fuel and air flow are
concerned. Besides, small engine pumper carbs tend to be kind of on/off
devices in that they idle OK and and run wide open well but don't do so
well in the mid range throttle settings. I suppose I could buy one but
I'm cheap. So, if there is room to invert the carb what else do I need
to worry about? Will the crankcase tend to get too hot since it will now
be above the cylinder? And lets say that the engine is not only inverted
but also turned around. Now the engine will be rotating the wrong way to
drive the bike forward. Since the engine is a two stroke it seems to me
that I will only need to change the ignition timing. I think this can be
done simply by broaching a new keyway in the spinning magnet flywheel.
The ignition is a fully electronic CDI type with no points. I assume the
ignition works by sensing the voltage rise in the magneto primary
winding as there is no other provision for detecting the position of the
flywheel magnet. Have I missed anything?
Thanks,
Eric

Worry about plug fouling. I don't know if it'll happen or not, but oil
drains down, and oil fouls plugs.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?
Thanks,
Eric
2 strokes have been mounted "upside-rown" in ultralight aircraft for
many years. Mounted that way they do tend to foul plugs and flood
easily when starting, but they generally run fine after starting.

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?
Thanks,
Eric

Model airplane 2 stroke motors are frequently mounted upside down and
run all right although if you flood one it might be a bit more
difficult to start and chainsaw run all right upside down.

As for running backward, I'm not sure of the efficiency as some modern
2 strokes use some pretty exotic porting that may be rotation
directional in nature. I'm leaning on model engine experience but some
glow plug designs of model engines seemed to run in either direction
with no problems and other, different in design, wouldn't seem to run
backwards at all.

But I don't think that you will do any mechanical damage by trying it.

--
cheers,

John B.

On Thu, 22 Oct 2015 08:53:44 +0700, John B. wrote:

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a 2
stroke bicycle engine upside down. Maybe upside down and backward. If I
did this the carb would need to be inverted because it is a float bowl
type carb. I suppose I could use a pumper type carb instead but I don't
know if I have one that is suitable as far as fuel and air flow are
concerned. Besides, small engine pumper carbs tend to be kind of on/off
devices in that they idle OK and and run wide open well but don't do so
well in the mid range throttle settings. I suppose I could buy one but
I'm cheap. So, if there is room to invert the carb what else do I need
to worry about? Will the crankcase tend to get too hot since it will now
be above the cylinder? And lets say that the engine is not only inverted
but also turned around. Now the engine will be rotating the wrong way to
drive the bike forward. Since the engine is a two stroke it seems to me
that I will only need to change the ignition timing. I think this can be
done simply by broaching a new keyway in the spinning magnet flywheel.
The ignition is a fully electronic CDI type with no points. I assume the
ignition works by sensing the voltage rise in the magneto primary
winding as there is no other provision for detecting the position of the
flywheel magnet. Have I missed anything?
Thanks,
Eric

Model airplane 2 stroke motors are frequently mounted upside down and
run all right although if you flood one it might be a bit more difficult
to start and chainsaw run all right upside down.

As for running backward, I'm not sure of the efficiency as some modern 2
strokes use some pretty exotic porting that may be rotation directional
in nature. I'm leaning on model engine experience but some glow plug
designs of model engines seemed to run in either direction with no
problems and other, different in design, wouldn't seem to run backwards
at all.

The rotation direction thing is what Ed was referring to -- most model
airplane 2-strokes have intake ports that are timed by the crank, and
that lead the piston by a considerable amount. This makes the engine
prefer to run in just one direction. Cox reed-valve engines are
direction agnostic, as are the really old piston-timed engines.

Weed-whacker and chainsaw motors are, to my knowledge, piston timed, with
the intake port to the crankshaft opened and closed by the skirt of the
piston rather than by the crank or a rotor attached to the crank. So,
they'll run pretty much the same in either direction, once you get the
spark timing sorted out.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Wed, 21 Oct 2015 14:01:25 -0700, etpm wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a 2
stroke bicycle engine upside down. Maybe upside down and backward. If I
did this the carb would need to be inverted because it is a float bowl
type carb. I suppose I could use a pumper type carb instead but I don't
know if I have one that is suitable as far as fuel and air flow are
concerned. Besides, small engine pumper carbs tend to be kind of on/off
devices in that they idle OK and and run wide open well but don't do so
well in the mid range throttle settings. I suppose I could buy one but
I'm cheap. So, if there is room to invert the carb what else do I need
to worry about? Will the crankcase tend to get too hot since it will now
be above the cylinder? And lets say that the engine is not only inverted
but also turned around. Now the engine will be rotating the wrong way to
drive the bike forward. Since the engine is a two stroke it seems to me
that I will only need to change the ignition timing. I think this can be
done simply by broaching a new keyway in the spinning magnet flywheel.
The ignition is a fully electronic CDI type with no points. I assume the
ignition works by sensing the voltage rise in the magneto primary
winding as there is no other provision for detecting the position of the
flywheel magnet. Have I missed anything?
Thanks,
Eric

Just a thought -- if you end up reversing rotation, make sure that
there's not some feature already on the flywheel to accommodate that. I
could see an engine company making it so you could just flip the flywheel
over, or move the magnet to a different spot to reverse rotation, just to
keep BOM costs down. You probably won't be so lucky, but keep your brain
engaged when you open it up.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Thu, 22 Oct 2015 00:00:13 -0500, Tim Wescott
wrote:

On Thu, 22 Oct 2015 08:53:44 +0700, John B. wrote:

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a 2
stroke bicycle engine upside down. Maybe upside down and backward. If I
did this the carb would need to be inverted because it is a float bowl
type carb. I suppose I could use a pumper type carb instead but I don't
know if I have one that is suitable as far as fuel and air flow are
concerned. Besides, small engine pumper carbs tend to be kind of on/off
devices in that they idle OK and and run wide open well but don't do so
well in the mid range throttle settings. I suppose I could buy one but
I'm cheap. So, if there is room to invert the carb what else do I need
to worry about? Will the crankcase tend to get too hot since it will now
be above the cylinder? And lets say that the engine is not only inverted
but also turned around. Now the engine will be rotating the wrong way to
drive the bike forward. Since the engine is a two stroke it seems to me
that I will only need to change the ignition timing. I think this can be
done simply by broaching a new keyway in the spinning magnet flywheel.
The ignition is a fully electronic CDI type with no points. I assume the
ignition works by sensing the voltage rise in the magneto primary
winding as there is no other provision for detecting the position of the
flywheel magnet. Have I missed anything?
Thanks,
Eric

Model airplane 2 stroke motors are frequently mounted upside down and
run all right although if you flood one it might be a bit more difficult
to start and chainsaw run all right upside down.

As for running backward, I'm not sure of the efficiency as some modern 2
strokes use some pretty exotic porting that may be rotation directional
in nature. I'm leaning on model engine experience but some glow plug
designs of model engines seemed to run in either direction with no
problems and other, different in design, wouldn't seem to run backwards
at all.

The rotation direction thing is what Ed was referring to -- most model
airplane 2-strokes have intake ports that are timed by the crank, and
that lead the piston by a considerable amount. This makes the engine
prefer to run in just one direction. Cox reed-valve engines are
direction agnostic, as are the really old piston-timed engines.

I'd really like to see the engine the OP is talking about. Chances are
that it's a piston-port engine, as most bike motors have been since
the beginning. My old O&R bike motor is a cross-scavenge, piston-port
engine -- the basic 2-stroke design that powered everything including
lawnmowers and ancient washing machines, and was used in all sorts of
applications where you're after low cost and smooth running, rather
than performance.


Weed-whacker and chainsaw motors are, to my knowledge, piston timed, with
the intake port to the crankshaft opened and closed by the skirt of the
piston rather than by the crank or a rotor attached to the crank. So,
they'll run pretty much the same in either direction, once you get the
spark timing sorted out.

I think that both piston-port and reed-valve intake have both been
used in chainsaws. Either one will allow an engine to run in either
direction, given the ignition timing issue discussed before.

--
Ed Huntress

wrote:
Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?

Is rebuilding an engine really the easier option here? I just can't
imagine that it is.

I have a bike with an engine strapped on. It's a decade old Golden Eagle
kit with the drive ring and belt and a 25cc Redmax weed wacker engine. The
only engine problems have been gas tank leaks from that ethanol **** in
the gas. It starts in negative temps, or with old gas. Very solid little
engine.

It sounds like you're going for the engine mounted inside the triangle of
the frame and not something strapped over the rear wheel though. The fake
motorcycle style is all I see these days. Never come across another belt
drive bike like I have yet.

On Thu, 22 Oct 2015 15:58:43 +0000 (UTC), Cydrome Leader
wrote:

wrote:
Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?

Is rebuilding an engine really the easier option here? I just can't
imagine that it is.

I have a bike with an engine strapped on. It's a decade old Golden Eagle
kit with the drive ring and belt and a 25cc Redmax weed wacker engine. The
only engine problems have been gas tank leaks from that ethanol **** in
the gas. It starts in negative temps, or with old gas. Very solid little
engine.

It sounds like you're going for the engine mounted inside the triangle of
the frame and not something strapped over the rear wheel though. The fake
motorcycle style is all I see these days. Never come across another belt
drive bike like I have yet.


The "Whizzer" motor bicycle, and motor kits for bicycles, was made
from around 1939 until about 2009 and there are some NOS still
available.
--
cheers,

John B.

John B. wrote:
On Thu, 22 Oct 2015 15:58:43 +0000 (UTC), Cydrome Leader
wrote:

wrote:
Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?

Is rebuilding an engine really the easier option here? I just can't
imagine that it is.

I have a bike with an engine strapped on. It's a decade old Golden Eagle
kit with the drive ring and belt and a 25cc Redmax weed wacker engine. The
only engine problems have been gas tank leaks from that ethanol **** in
the gas. It starts in negative temps, or with old gas. Very solid little
engine.

It sounds like you're going for the engine mounted inside the triangle of
the frame and not something strapped over the rear wheel though. The fake
motorcycle style is all I see these days. Never come across another belt
drive bike like I have yet.


The "Whizzer" motor bicycle, and motor kits for bicycles, was made
from around 1939 until about 2009 and there are some NOS still
available.

That's the style of kit I see in Chicago. I still prefer the leafblower
type as you just put a plastic bag over it and nobody knows it's a bike
with an engine.

On Thu, 22 Oct 2015 09:03:57 -0400, Ed Huntress wrote:

On Thu, 22 Oct 2015 00:00:13 -0500, Tim Wescott
wrote:

On Thu, 22 Oct 2015 08:53:44 +0700, John B. wrote:

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?
Thanks,
Eric

Model airplane 2 stroke motors are frequently mounted upside down and
run all right although if you flood one it might be a bit more
difficult to start and chainsaw run all right upside down.

As for running backward, I'm not sure of the efficiency as some modern
2 strokes use some pretty exotic porting that may be rotation
directional in nature. I'm leaning on model engine experience but some
glow plug designs of model engines seemed to run in either direction
with no problems and other, different in design, wouldn't seem to run
backwards at all.

The rotation direction thing is what Ed was referring to -- most model
airplane 2-strokes have intake ports that are timed by the crank, and
that lead the piston by a considerable amount. This makes the engine
prefer to run in just one direction. Cox reed-valve engines are
direction agnostic, as are the really old piston-timed engines.

I'd really like to see the engine the OP is talking about.

Me, too -- Eric, can you post a picture someplace, or a link to the
seller's website?

Chances are
that it's a piston-port engine, as most bike motors have been since the
beginning. My old O&R bike motor is a cross-scavenge, piston-port engine
-- the basic 2-stroke design that powered everything including
lawnmowers and ancient washing machines, and was used in all sorts of
applications where you're after low cost and smooth running, rather than
performance.


Weed-whacker and chainsaw motors are, to my knowledge, piston timed,
with the intake port to the crankshaft opened and closed by the skirt of
the piston rather than by the crank or a rotor attached to the crank.
So, they'll run pretty much the same in either direction, once you get
the spark timing sorted out.

I think that both piston-port and reed-valve intake have both been used
in chainsaws.

I could see that -- chainsaws have a bit more need to be high performance
in a small package than a lot of other 2-stroke applications. I suppose
I wouldn't even be surprised at a crank-timed one (I'm kind of surprised
that crank-timed 2-strokes only seem to be ubiquitous in model airplane
use, and even there the really big ones are piston-timed, either because
they've been repurposed from weed-whacker engines, or because they've
been re-designed from such engines).

Either one will allow an engine to run in either
direction, given the ignition timing issue discussed before.


--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Fri, 23 Oct 2015 12:27:13 -0500, Tim Wescott
wrote:

On Thu, 22 Oct 2015 09:03:57 -0400, Ed Huntress wrote:

On Thu, 22 Oct 2015 00:00:13 -0500, Tim Wescott
wrote:

On Thu, 22 Oct 2015 08:53:44 +0700, John B. wrote:

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?
Thanks,
Eric

Model airplane 2 stroke motors are frequently mounted upside down and
run all right although if you flood one it might be a bit more
difficult to start and chainsaw run all right upside down.

As for running backward, I'm not sure of the efficiency as some modern
2 strokes use some pretty exotic porting that may be rotation
directional in nature. I'm leaning on model engine experience but some
glow plug designs of model engines seemed to run in either direction
with no problems and other, different in design, wouldn't seem to run
backwards at all.

The rotation direction thing is what Ed was referring to -- most model
airplane 2-strokes have intake ports that are timed by the crank, and
that lead the piston by a considerable amount. This makes the engine
prefer to run in just one direction. Cox reed-valve engines are
direction agnostic, as are the really old piston-timed engines.

I'd really like to see the engine the OP is talking about.

Me, too -- Eric, can you post a picture someplace, or a link to the
seller's website?

Chances are
that it's a piston-port engine, as most bike motors have been since the
beginning. My old O&R bike motor is a cross-scavenge, piston-port engine
-- the basic 2-stroke design that powered everything including
lawnmowers and ancient washing machines, and was used in all sorts of
applications where you're after low cost and smooth running, rather than
performance.


Weed-whacker and chainsaw motors are, to my knowledge, piston timed,
with the intake port to the crankshaft opened and closed by the skirt of
the piston rather than by the crank or a rotor attached to the crank.
So, they'll run pretty much the same in either direction, once you get
the spark timing sorted out.

I think that both piston-port and reed-valve intake have both been used
in chainsaws.

I could see that -- chainsaws have a bit more need to be high performance
in a small package than a lot of other 2-stroke applications. I suppose
I wouldn't even be surprised at a crank-timed one (I'm kind of surprised
that crank-timed 2-strokes only seem to be ubiquitous in model airplane
use, and even there the really big ones are piston-timed, either because
they've been repurposed from weed-whacker engines, or because they've
been re-designed from such engines).

I've actually had my hands on only two rotary-valve 2-strokes: my old
McCoy Red Head .35, which had a hollow crank with a window in one side
for a port (very strange), and a Yamaha 175 dirt bike. I put a "Git
Kit" in that bike, which included a new rotary-port disk, with
different timing.

--
Ed Huntress

Either one will allow an engine to run in either
direction, given the ignition timing issue discussed before.

On Thu, 22 Oct 2015 09:03:57 -0400, Ed Huntress
wrote:

On Thu, 22 Oct 2015 00:00:13 -0500, Tim Wescott
wrote:

On Thu, 22 Oct 2015 08:53:44 +0700, John B. wrote:

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a 2
stroke bicycle engine upside down. Maybe upside down and backward. If I
did this the carb would need to be inverted because it is a float bowl
type carb. I suppose I could use a pumper type carb instead but I don't
know if I have one that is suitable as far as fuel and air flow are
concerned. Besides, small engine pumper carbs tend to be kind of on/off
devices in that they idle OK and and run wide open well but don't do so
well in the mid range throttle settings. I suppose I could buy one but
I'm cheap. So, if there is room to invert the carb what else do I need
to worry about? Will the crankcase tend to get too hot since it will now
be above the cylinder? And lets say that the engine is not only inverted
but also turned around. Now the engine will be rotating the wrong way to
drive the bike forward. Since the engine is a two stroke it seems to me
that I will only need to change the ignition timing. I think this can be
done simply by broaching a new keyway in the spinning magnet flywheel.
The ignition is a fully electronic CDI type with no points. I assume the
ignition works by sensing the voltage rise in the magneto primary
winding as there is no other provision for detecting the position of the
flywheel magnet. Have I missed anything?
Thanks,
Eric

Model airplane 2 stroke motors are frequently mounted upside down and
run all right although if you flood one it might be a bit more difficult
to start and chainsaw run all right upside down.

As for running backward, I'm not sure of the efficiency as some modern 2
strokes use some pretty exotic porting that may be rotation directional
in nature. I'm leaning on model engine experience but some glow plug
designs of model engines seemed to run in either direction with no
problems and other, different in design, wouldn't seem to run backwards
at all.

The rotation direction thing is what Ed was referring to -- most model
airplane 2-strokes have intake ports that are timed by the crank, and
that lead the piston by a considerable amount. This makes the engine
prefer to run in just one direction. Cox reed-valve engines are
direction agnostic, as are the really old piston-timed engines.

I'd really like to see the engine the OP is talking about. Chances are
that it's a piston-port engine, as most bike motors have been since
the beginning. My old O&R bike motor is a cross-scavenge, piston-port
engine -- the basic 2-stroke design that powered everything including
lawnmowers and ancient washing machines, and was used in all sorts of
applications where you're after low cost and smooth running, rather
than performance.


Weed-whacker and chainsaw motors are, to my knowledge, piston timed, with
the intake port to the crankshaft opened and closed by the skirt of the
piston rather than by the crank or a rotor attached to the crank. So,
they'll run pretty much the same in either direction, once you get the
spark timing sorted out.

I think that both piston-port and reed-valve intake have both been
used in chainsaws. Either one will allow an engine to run in either
direction, given the ignition timing issue discussed before.
ED-the engine is piston ported. These engines are ubiquitous online. I
know they are not all made in the same factories but they are all
similar. See the link:
www.californiamotorbikes.com
I had, years and years ago, a Yamaha 80 that used the rotarty valve
setup. It was interesting because the carb was inside the engine case
on the right side. I think Kawasaki made a similar engine. Also
interesting was the fact that there was a Honda motorcycle that not
only looked a whole lot like the Yamaha but had some parts that were
interchangeable. Like the front forks. These weren't the telescoping
type forks so to swap forks the whole front end needed to be changed.
Eric

On Fri, 23 Oct 2015 12:54:23 -0700, wrote:

On Thu, 22 Oct 2015 09:03:57 -0400, Ed Huntress
wrote:

On Thu, 22 Oct 2015 00:00:13 -0500, Tim Wescott
wrote:

On Thu, 22 Oct 2015 08:53:44 +0700, John B. wrote:

On Wed, 21 Oct 2015 14:01:25 -0700, wrote:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a 2
stroke bicycle engine upside down. Maybe upside down and backward. If I
did this the carb would need to be inverted because it is a float bowl
type carb. I suppose I could use a pumper type carb instead but I don't
know if I have one that is suitable as far as fuel and air flow are
concerned. Besides, small engine pumper carbs tend to be kind of on/off
devices in that they idle OK and and run wide open well but don't do so
well in the mid range throttle settings. I suppose I could buy one but
I'm cheap. So, if there is room to invert the carb what else do I need
to worry about? Will the crankcase tend to get too hot since it will now
be above the cylinder? And lets say that the engine is not only inverted
but also turned around. Now the engine will be rotating the wrong way to
drive the bike forward. Since the engine is a two stroke it seems to me
that I will only need to change the ignition timing. I think this can be
done simply by broaching a new keyway in the spinning magnet flywheel.
The ignition is a fully electronic CDI type with no points. I assume the
ignition works by sensing the voltage rise in the magneto primary
winding as there is no other provision for detecting the position of the
flywheel magnet. Have I missed anything?
Thanks,
Eric

Model airplane 2 stroke motors are frequently mounted upside down and
run all right although if you flood one it might be a bit more difficult
to start and chainsaw run all right upside down.

As for running backward, I'm not sure of the efficiency as some modern 2
strokes use some pretty exotic porting that may be rotation directional
in nature. I'm leaning on model engine experience but some glow plug
designs of model engines seemed to run in either direction with no
problems and other, different in design, wouldn't seem to run backwards
at all.

The rotation direction thing is what Ed was referring to -- most model
airplane 2-strokes have intake ports that are timed by the crank, and
that lead the piston by a considerable amount. This makes the engine
prefer to run in just one direction. Cox reed-valve engines are
direction agnostic, as are the really old piston-timed engines.

I'd really like to see the engine the OP is talking about. Chances are
that it's a piston-port engine, as most bike motors have been since
the beginning. My old O&R bike motor is a cross-scavenge, piston-port
engine -- the basic 2-stroke design that powered everything including
lawnmowers and ancient washing machines, and was used in all sorts of
applications where you're after low cost and smooth running, rather
than performance.


Weed-whacker and chainsaw motors are, to my knowledge, piston timed, with
the intake port to the crankshaft opened and closed by the skirt of the
piston rather than by the crank or a rotor attached to the crank. So,
they'll run pretty much the same in either direction, once you get the
spark timing sorted out.

I think that both piston-port and reed-valve intake have both been
used in chainsaws. Either one will allow an engine to run in either
direction, given the ignition timing issue discussed before.
ED-the engine is piston ported. These engines are ubiquitous online. I
know they are not all made in the same factories but they are all
similar. See the link:
www.californiamotorbikes.com

Aha. Yes, your basic piston-port 2-stroke.

I had, years and years ago, a Yamaha 80 that used the rotarty valve
setup. It was interesting because the carb was inside the engine case
on the right side. I think Kawasaki made a similar engine. Also
interesting was the fact that there was a Honda motorcycle that not
only looked a whole lot like the Yamaha but had some parts that were
interchangeable. Like the front forks. These weren't the telescoping
type forks so to swap forks the whole front end needed to be changed.
Eric

There sure were a lot of oddities in those early Japanese bikes. They
were pretty clever.

--
Ed Huntress

On Fri, 23 Oct 2015 16:50:45 +0000 (UTC), Cydrome Leader
wrote:

John B. wrote:
On Thu, 22 Oct 2015 15:58:43 +0000 (UTC), Cydrome Leader
wrote:

wrote:
Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?

Is rebuilding an engine really the easier option here? I just can't
imagine that it is.

I have a bike with an engine strapped on. It's a decade old Golden Eagle
kit with the drive ring and belt and a 25cc Redmax weed wacker engine. The
only engine problems have been gas tank leaks from that ethanol **** in
the gas. It starts in negative temps, or with old gas. Very solid little
engine.

It sounds like you're going for the engine mounted inside the triangle of
the frame and not something strapped over the rear wheel though. The fake
motorcycle style is all I see these days. Never come across another belt
drive bike like I have yet.


The "Whizzer" motor bicycle, and motor kits for bicycles, was made
from around 1939 until about 2009 and there are some NOS still
available.

That's the style of kit I see in Chicago. I still prefer the leafblower
type as you just put a plastic bag over it and nobody knows it's a bike
with an engine.

Don't your "plastic bag" make a funny noise when you are driving?
--
cheers,

John B.

John B. wrote:
On Fri, 23 Oct 2015 16:50:45 +0000 (UTC), Cydrome Leader
wrote:

John B. wrote:
On Thu, 22 Oct 2015 15:58:43 +0000 (UTC), Cydrome Leader
wrote:

wrote:
Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?

Is rebuilding an engine really the easier option here? I just can't
imagine that it is.

I have a bike with an engine strapped on. It's a decade old Golden Eagle
kit with the drive ring and belt and a 25cc Redmax weed wacker engine. The
only engine problems have been gas tank leaks from that ethanol **** in
the gas. It starts in negative temps, or with old gas. Very solid little
engine.

It sounds like you're going for the engine mounted inside the triangle of
the frame and not something strapped over the rear wheel though. The fake
motorcycle style is all I see these days. Never come across another belt
drive bike like I have yet.


The "Whizzer" motor bicycle, and motor kits for bicycles, was made
from around 1939 until about 2009 and there are some NOS still
available.

That's the style of kit I see in Chicago. I still prefer the leafblower
type as you just put a plastic bag over it and nobody knows it's a bike
with an engine.

Don't your "plastic bag" make a funny noise when you are driving?

The bag is for bringing it inside buildings where bikes are ok but not
other "vehicles".

On Sun, 25 Oct 2015 07:38:24 +0000, Charlie+ wrote:

On Wed, 21 Oct 2015 14:01:25 -0700, wrote as underneath
:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?
Thanks,
Eric

I just wonder if the ignition in a point-less system will work so well
if the flywheel rotation is reversed? With the points type magneto it
makes no difference but with the pointless type the system is optimised
with a mapped timed firing by potted electronic components built into
the coil assembly (hence the modern easy start 2-stroke systems) and the
coil can be much smaller and cheaper as the UHV is generated by
electronic circuitry rather than directly by the magneto. So- maybe the
mapping will not make the corrections in the right direction etc.? I
would anyway try running it in reverse with an electric drill etc. to
see how the ignition might work if you do this?! Just a thaught - I
havnt tried so absolutely no actual experience with running this type of
ignition in reverse, someone else here might have?! C+
Thanks for the reply Charlie. It would be a good idea to see when the
spark occurs. If, for example, it happens at 12 degrees before TDC
then I need to make sure it happens on the other side of TDC since the
crankshaft will be spinning the other way. Using a drill to spin the
engine so I can watch the spark timing is a good idea. The electronics
for the ignition are located away from the engine, it appears that the
magneto coil is only a coil and has no device for sensing crankshaft
position, so all the timing is done in the black box that is mounted
away from the engine. But I still need to see what the timing is to
make sure I get it right when reversing the engine.
Eric

On Mon, 26 Oct 2015 14:06:48 -0700, wrote:

On Sun, 25 Oct 2015 07:38:24 +0000, Charlie+ wrote:

On Wed, 21 Oct 2015 14:01:25 -0700, wrote as underneath
:

Because of the size and the way my bicycle frame is shaped it may be
more convenient, strictly from a mechanical point of view, to mount a
2 stroke bicycle engine upside down. Maybe upside down and backward.
If I did this the carb would need to be inverted because it is a float
bowl type carb. I suppose I could use a pumper type carb instead but I
don't know if I have one that is suitable as far as fuel and air flow
are concerned. Besides, small engine pumper carbs tend to be kind of
on/off devices in that they idle OK and and run wide open well but
don't do so well in the mid range throttle settings. I suppose I could
buy one but I'm cheap. So, if there is room to invert the carb what
else do I need to worry about? Will the crankcase tend to get too hot
since it will now be above the cylinder? And lets say that the engine
is not only inverted but also turned around. Now the engine will be
rotating the wrong way to drive the bike forward. Since the engine is
a two stroke it seems to me that I will only need to change the
ignition timing. I think this can be done simply by broaching a new
keyway in the spinning magnet flywheel. The ignition is a fully
electronic CDI type with no points. I assume the ignition works by
sensing the voltage rise in the magneto primary winding as there is no
other provision for detecting the position of the flywheel magnet.
Have I missed anything?
Thanks,
Eric

I just wonder if the ignition in a point-less system will work so well
if the flywheel rotation is reversed? With the points type magneto it
makes no difference but with the pointless type the system is optimised
with a mapped timed firing by potted electronic components built into
the coil assembly (hence the modern easy start 2-stroke systems) and the
coil can be much smaller and cheaper as the UHV is generated by
electronic circuitry rather than directly by the magneto. So- maybe the
mapping will not make the corrections in the right direction etc.? I
would anyway try running it in reverse with an electric drill etc. to
see how the ignition might work if you do this?! Just a thaught - I
havnt tried so absolutely no actual experience with running this type of
ignition in reverse, someone else here might have?! C+
Thanks for the reply Charlie. It would be a good idea to see when the
spark occurs. If, for example, it happens at 12 degrees before TDC
then I need to make sure it happens on the other side of TDC since the
crankshaft will be spinning the other way. Using a drill to spin the
engine so I can watch the spark timing is a good idea. The electronics
for the ignition are located away from the engine, it appears that the
magneto coil is only a coil and has no device for sensing crankshaft
position, so all the timing is done in the black box that is mounted
away from the engine. But I still need to see what the timing is to
make sure I get it right when reversing the engine.
Eric

Many of the very simple old 2-strokes just relied on the magnet
*leaving* the field to time the spark. Sort of time, that is. g As
the motor speeds up, the spark timing actually can advance a few
degrees that way.

You may be able to tell from the relative position of the magnet in
the flywheel, to the magneto coil, where the timing is. In any case,
it will give you guidance about setting it on the opposite side of TDC
if you want to run the motor in reverse.

--
Ed Huntress

Many of the very simple old 2-strokes just relied on the magnet
*leaving* the field to time the spark. Sort of time, that is. g As
the motor speeds up, the spark timing actually can advance a few
degrees that way.

You may be able to tell from the relative position of the magnet in
the flywheel, to the magneto coil, where the timing is. In any case,
it will give you guidance about setting it on the opposite side of TDC
if you want to run the motor in reverse.
I have worked on a lot of old two stroke motors, motors with cast iron
pistons, completely unbalanced cranks, and grease cups to lubricate
and seal the crankshaft where it exits the crankcase. And I have never
seen an ignition like that. The oldest magnetos I have seen had points
of some type. I can't see how leaving the magnetic field would cause a
spark. Can you explain it?
Eric

On Mon, 26 Oct 2015 15:58:01 -0700, wrote:



Many of the very simple old 2-strokes just relied on the magnet
*leaving* the field to time the spark. Sort of time, that is. g As
the motor speeds up, the spark timing actually can advance a few
degrees that way.

You may be able to tell from the relative position of the magnet in
the flywheel, to the magneto coil, where the timing is. In any case,
it will give you guidance about setting it on the opposite side of TDC
if you want to run the motor in reverse.
I have worked on a lot of old two stroke motors, motors with cast iron
pistons, completely unbalanced cranks, and grease cups to lubricate
and seal the crankshaft where it exits the crankcase. And I have never
seen an ignition like that. The oldest magnetos I have seen had points
of some type. I can't see how leaving the magnetic field would cause a
spark. Can you explain it?
Eric

Oh, boy, the memory is the second thing to go. g I was confusing
myself with the old low-tension systems with the points in the
cylinder (the "make and break" systems) that we were talking about
here a couple of weeks ago. I got them mixed up in my memory.

As for the relationship of magnet to coil and the timing, though, that
does apply. That will determine the peak output. However, the points
have to open close to that peak, too.

Sheesh. Sorry to be misleading. I hate when that happens.

--
Ed Huntress

On Mon, 26 Oct 2015 19:52:29 -0400, Ed Huntress
wrote:

On Mon, 26 Oct 2015 15:58:01 -0700, wrote:



Many of the very simple old 2-strokes just relied on the magnet
*leaving* the field to time the spark. Sort of time, that is. g As
the motor speeds up, the spark timing actually can advance a few
degrees that way.

You may be able to tell from the relative position of the magnet in
the flywheel, to the magneto coil, where the timing is. In any case,
it will give you guidance about setting it on the opposite side of TDC
if you want to run the motor in reverse.
I have worked on a lot of old two stroke motors, motors with cast iron
pistons, completely unbalanced cranks, and grease cups to lubricate
and seal the crankshaft where it exits the crankcase. And I have never
seen an ignition like that. The oldest magnetos I have seen had points
of some type. I can't see how leaving the magnetic field would cause a
spark. Can you explain it?
Eric

Oh, boy, the memory is the second thing to go. g I was confusing
myself with the old low-tension systems with the points in the
cylinder (the "make and break" systems) that we were talking about
here a couple of weeks ago. I got them mixed up in my memory.

As for the relationship of magnet to coil and the timing, though, that
does apply. That will determine the peak output. However, the points
have to open close to that peak, too.

Sheesh. Sorry to be misleading. I hate when that happens.
Yeah, I know all about that failing memory crap. I did know about the
points and magnet timing too. Which is why, for example, when a points
type ignition on a Briggs and Stratton engine won't spark when the
flywheel key shears. Even if it shears only about 1/2 of the key
width they usually won't fire because the spark will be too weak.
Eric

On Tue, 27 Oct 2015 07:44:33 +0000, Charlie+ wrote:

On Mon, 26 Oct 2015 14:06:48 -0700, wrote as underneath
:

snip

I just wonder if the ignition in a point-less system will work so well
if the flywheel rotation is reversed? With the points type magneto it
makes no difference but with the pointless type the system is optimised
with a mapped timed firing by potted electronic components built into
the coil assembly (hence the modern easy start 2-stroke systems) and the
coil can be much smaller and cheaper as the UHV is generated by
electronic circuitry rather than directly by the magneto. So- maybe the
mapping will not make the corrections in the right direction etc.? I
would anyway try running it in reverse with an electric drill etc. to
see how the ignition might work if you do this?! Just a thaught - I
havnt tried so absolutely no actual experience with running this type of
ignition in reverse, someone else here might have?! C+

Thanks for the reply Charlie. It would be a good idea to see when the
spark occurs. If, for example, it happens at 12 degrees before TDC
then I need to make sure it happens on the other side of TDC since the
crankshaft will be spinning the other way. Using a drill to spin the
engine so I can watch the spark timing is a good idea. The electronics
for the ignition are located away from the engine, it appears that the
magneto coil is only a coil and has no device for sensing crankshaft
position, so all the timing is done in the black box that is mounted
away from the engine. But I still need to see what the timing is to
make sure I get it right when reversing the engine.
Eric

These modern pointless systems have two hall effect detectors (built
into the magneto coil system) to detect the speed of rotation and fix
the firing point in software ... and also by default the direction of
rotation I assume!! Your split box system I havnt come across - It must
still have the timing sense from the coil unit somehow, probably a
multiple cable connection to the cdi box. The modern ones only have the
plug lead and a kill switch wire, nothing else that shows externally...
I happened to have a modern chainsaw partly in bits yesterday so I
followed my own advice to you and span it in reverse with the ignition
on and watched the plug: correct direction, nice fat spark : reverse
direction, nothing... so be warned!!
I only ran it at speeds enough to get the spark to work properly and
then the same speed in reverse - no test to destructio!! No point in
wrecking a perfectly good chainsaw motor! If I were doing this I would
correct the position of the coil or the flywheel firing point AND also
turn the coil unit upside down so that it all works in the directions as
designed... maybe an oscilloscope and metalwork will be involved and
there maybe space problems! Could be interesting, keep us informed! At
full chat a high speed 2-stroke can be timed near 30 degrees BTDC I
believe! C+
Charlie,
I have a couple electronic points replacement modules made for the
typical lawn mower engine that used points. To use them the wire to
the points is cut and connected to the module instead of the points.
The only other connection for the module is ground. Anyway, these
modules work great and I believe the ignition on the engine we're
talking about works the same way. But I was wondering if the direction
the coil is wound in relation to the rotation direction of the magnet
would make any difference. Fortunately it looks like the magneto coil
can be inverted like you suggest. So if coil direction matters it
looks like I'll be OK.
Eric

Tim Wescott writes:


Weed-whacker and chainsaw motors are, to my knowledge, piston timed, with
the intake port to the crankshaft opened and closed by the skirt of the
piston rather than by the crank or a rotor attached to the crank. So,
they'll run pretty much the same in either direction, once you get the
spark timing sorted out.

The classic 3 cylinder 2-cycle Saab 95 would run either way. Car Talk
once had a Puzzler on how one could beat a muscle car in a drag race.
The answer was "backwards..." as the Saab could be started the other
way and have 4-speeds of reverse...

--
A host is a host from coast to
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On Thu, 10 Dec 2015 19:40:30 +0000 (UTC), David Lesher
wrote:

Tim Wescott writes:


Weed-whacker and chainsaw motors are, to my knowledge, piston timed, with
the intake port to the crankshaft opened and closed by the skirt of the
piston rather than by the crank or a rotor attached to the crank. So,
they'll run pretty much the same in either direction, once you get the
spark timing sorted out.

The classic 3 cylinder 2-cycle Saab 95 would run either way. Car Talk
once had a Puzzler on how one could beat a muscle car in a drag race.
The answer was "backwards..." as the Saab could be started the other
way and have 4-speeds of reverse...

In my novice race at Lime Rock Park, in the late '60s, I got stuck
behind a Saab 93 that had been race-tuned (squared ports, etc.). His
secret weapon was that he smoked out anyone who tried to pass him.

--
Ed Huntress

I have a weedeat, thats the brand name on it. I put it on my back of my bike. I just happen to ha e a bike that had a braket that worked to put it on ther. Welk after i had it all set up realized that its upsidedown.. And it was firing and a few times acted lke it was going to start... But never did... Now it is on the left side mounted on the bike..i spun the carburetor on it thinking it would work that way... But still failed to start... Thus is the firstbone i have made.. So any ideas on what i need to do... I tried everything.. Cleaned everything... Still has spark..tried spraying gas in the carburetor.... Anyone have ideas... Please let me lnow thanks

On 01/09/2019 10:24 AM, wrote:
I have a weedeat, thats the brand name on it.

That's a crummy brand.

I put it on my back of my bike. I just happen to ha e a bike that had
a braket that worked to put it on ther. Welk after i had it all set
up realized that its upsidedown.. And it was firing and a few times
acted lke it was going to start... But never did... Now it is on the
left side mounted on the bike..i spun the carburetor on it thinking
it would work that way... But still failed to start... Thus is the
firstbone i have made.. So any ideas on what i need to do... I tried
everything.. Cleaned everything... Still has spark..tried spraying
gas in the carburetor.... Anyone have ideas... Please let me lnow
thanks

Get an Echo.

On Thu, 10 Jan 2019 08:36:01 -0800, Junco wrote:

On 01/09/2019 10:24 AM, wrote:
I have a weedeat, thats the brand name on it.

That's a crummy brand.

I put it on my back of my bike. I just happen to ha e a bike that had
a braket that worked to put it on ther. Welk after i had it all set
up realized that its upsidedown.. And it was firing and a few times
acted lke it was going to start... But never did... Now it is on the
left side mounted on the bike..i spun the carburetor on it thinking
it would work that way... But still failed to start... Thus is the
firstbone i have made.. So any ideas on what i need to do... I tried
everything.. Cleaned everything... Still has spark..tried spraying
gas in the carburetor.... Anyone have ideas... Please let me lnow
thanks

Get an Echo.
There is no such thing as "upside down" for a 2 stroker. Just the
carb (if it is a float type)

If you have compression, fuel and air in the right ratio, and spark it
will run.

The only issue with "plug down" installation is it is easy to
wet-foul the plug