Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #21   Report Post  
Old October 26th 15, 11:52 PM posted to rec.crafts.metalworking
external usenet poster
 
First recorded activity by DIYBanter: Nov 2006
Posts: 12,535
Default Mount a 2 stroke upside down?

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

  #22   Report Post  
Old October 27th 15, 12:30 AM posted to rec.crafts.metalworking
external usenet poster
 
First recorded activity by DIYBanter: Apr 2008
Posts: 1,995
Default Mount a 2 stroke upside down?

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
  #23   Report Post  
Old October 27th 15, 04:32 PM posted to rec.crafts.metalworking
external usenet poster
 
First recorded activity by DIYBanter: Apr 2008
Posts: 1,995
Default Mount a 2 stroke upside down?

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
  #24   Report Post  
Old December 10th 15, 07:40 PM posted to rec.crafts.metalworking
external usenet poster
 
First recorded activity by DIYBanter: Jan 2007
Posts: 662
Default Mount a 2 stroke upside down?

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
  #25   Report Post  
Old December 10th 15, 07:49 PM posted to rec.crafts.metalworking
external usenet poster
 
First recorded activity by DIYBanter: Nov 2006
Posts: 12,535
Default Mount a 2 stroke upside down?

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


  #26   Report Post  
Old January 9th 19, 06:24 PM posted to rec.crafts.metalworking
external usenet poster
 
First recorded activity by DIYBanter: Jan 2019
Posts: 1
Default Mount a 2 stroke upside down?

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
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
SIde Mount Garage Door Opener - Does One Exist? Can I use GenieStandard Mount? Billy Home Ownership 5 October 20th 09 01:58 PM
Radical upside down Craftsman 10" Radial Sled Saw / Upside down tablesaw BoyntonStu Home Repair 0 April 18th 08 01:16 PM
My radical upside down Craftsman 10" Radial Sled Saw / Upside downtable saw BoyntonStu Woodworking 0 April 18th 08 12:21 PM
My radical upside down Craftsman 10" Radial Sled Saw / Upside downtable saw BoyntonStu Woodworking 0 April 18th 08 12:20 PM
Mount Board Buddies upside down ? Folklore Woodworking 8 October 13th 05 03:09 PM


All times are GMT +1. The time now is 03:51 AM.

Powered by vBulletin® Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"

 

Copyright © 2017