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Old October 21st 15, 10:01 PM posted to rec.crafts.metalworking
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Default Mount a 2 stroke upside down?

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

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Old October 21st 15, 10:24 PM posted to rec.crafts.metalworking
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Default Mount a 2 stroke upside down?

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
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Old October 21st 15, 10:28 PM posted to rec.crafts.metalworking
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Posts: 223
Default Mount a 2 stroke upside down?

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
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Old October 22nd 15, 01:32 AM posted to rec.crafts.metalworking
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Posts: 18,546
Default Mount a 2 stroke upside down?

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.
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Old October 22nd 15, 02:53 AM posted to rec.crafts.metalworking
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Posts: 194
Default Mount a 2 stroke upside down?

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.



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Old October 22nd 15, 06:00 AM posted to rec.crafts.metalworking
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Posts: 223
Default Mount a 2 stroke upside down?

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
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Old October 22nd 15, 06:02 AM posted to rec.crafts.metalworking
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Posts: 223
Default Mount a 2 stroke upside down?

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
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Old October 22nd 15, 02:03 PM posted to rec.crafts.metalworking
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Posts: 12,540
Default Mount a 2 stroke upside down?

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
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Old October 22nd 15, 04:58 PM posted to rec.crafts.metalworking
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Posts: 1,832
Default Mount a 2 stroke upside down?

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.


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Old October 23rd 15, 01:57 AM posted to rec.crafts.metalworking
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Posts: 194
Default Mount a 2 stroke upside down?

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.



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