2 stroke running in reverse

alkllimike · Jun 1, 2011

Is there any person on this forum that has reversed the direction of rotate of a 2 stoke China Girl engine commonly used on this motor bike? I know that a 2 stroke engine can run in either direction but I feel in order to do that the ignition timing must be changed for the engine to have the same power. If some person has accomplished that how did they do it and was there any negative effect?

I am wanting to mount a 60 cc 2 stroke on a recumbent trike and drive the rear wheels. The engine will be facing to the rear and driving a jack shaft that in turn will drive the wheel but the rotation will be reverse for the trike and I don't want to gear reverse the direction if I can retime the engine and have the engine rotate the direction I need. Mike

dmb · Jun 1, 2011

maybe if you put the magnet backwards? pulling the chain backwards???? how about a countershaft of some sort? i have seen inline 2 stroke detroit diesels run backwards, not very good. timing was wrong and the oil pump dont work, but they will run.

GearNut · Jun 1, 2011

The ignition timing would need to be hyper advanced to make it run backwards.
There is also a little bit more to it than that too.
Two-stroke engine - Wikipedia, the free encyclopedia
If I am not mistaken, the stock timing is approx. 19* BTDC. If you advance it to say....29* it would run backwards, but I don't know where the sweet spot would be for it to run well backwards.
I have yet to read on this forum or any of the other forums of anyone trying to run a China Girl backwards. Sorry I cannot be of more help to you.

Just running silly ideas in my head, What would happen if you were to install the mag rotor onto the crankshaft backwards and the mag coil up-side-down? Or perhaps some combination of all that? I know that you would have clearance issues between the mag coil and the crankcase as the coil windings are made offset in relation to the center line of the coil frame. Perhaps some careful grinding and spacers would accomplish it? I don't really know....... Just rambling out ideas here.

oldsub · Jun 2, 2011

Just thinging about 2 cycle engines, smaller kind like for power saws, blowers and weed eaters. On these you could just pull the flywheel and file a different keyway which would place the flywheel in the correct position. I don't see why it wouldn't run backwards.

You would have this problem, all bolts or thread would start to backoff because the engine is turning that way. Second your fins for cooling would also be in the wrong position.

Best of luck to you and your project.

oldsub

sketchman · Jun 2, 2011

Now this is interesting. You could have a shift kit without the jackshaft. Just mount the engine backwards and presto. Chain would be pointing right where you need it. Very interesting. Some loctite and it could work. Huh.

DaveC · Jun 2, 2011

All it would take is figuring where to cut a new keyway. These motors actually fire twice every revolution. They fire at 19 degrees BBDC, too. It's the notches in the magnet that triggers the CD to fire, that's what is timed. There are two notches so there are two timed events every revolution. It's just there's nothing to burn, any fuel has to be compressed or the spark has nothing to ignite.

This would be cool with the jug reversed, too

alkllimike · Jun 12, 2011

Thank guys for the replies. I have some good food for thought. Mike

DuctTapedGoat · Jun 14, 2011

Easy stuff to run it backwards. Grind everything down and hook your clutch and sprocket up to the fly wheel's first gear (20T).

sketchman · Jun 14, 2011

^Uhh, until you actually reverse the operation of the engine, you'd be driving backwards like that.

Or am I misunderstanding?

F_Rod81 · Jun 14, 2011

sounds interesting

DuctTapedGoat · Jun 14, 2011

Sketchman: You're entirely right - I'm just saying that's the easiest way I can think to get it in reverse at all. Same thing with changing the ignition timing, unless there's a quickchange option on the keyway.

Al.Fisherman · Jun 14, 2011

Ummmm this reminds me back when I was in High School, of a 2 cycle car that was built to run backwards...This car had no reverse. In order to go into reverse, you stopped the car, turned the ignition off, and restarted it in the reverse position. I can't for the life of me, remember its name. It was made in Europe somewhere. It was a funny car, someone that I knew, his friend brought it from I think Great Britain. So, Yes, It is possible to run a 2 cycle backwards.

DuctTapedGoat · Jun 14, 2011

I just tried push starting backwards for about 5 minutes and then I fell over on the bike.

So we know NOT to do that one.

Though, I might be onto something.

dmb · Jun 14, 2011

don't forget to use a helmet! maybe all the time...

GearNut · Jun 14, 2011

Just wear it backwards while riding backwards. You can't be too careful!

Greybeard · Jun 14, 2011

Most gas engine Golf carts use 2 stroke engines, and run backwards to go backwards. A quite a few outboard 2 strokes, mostly from Mercury, were built without a reversing gearbox. You turned them off, pulled the trottle back and restarted them "backwards". When you pulled the throttle back to the reversing position it just moved the timing back into a retarded posistion, and spun the starter backwards. It works very well.

halfevil333 · Jun 15, 2011

GearNut said:
The ignition timing would need to be hyper advanced to make it run backwards.
There is also a little bit more to it than that too.
Two-stroke engine - Wikipedia, the free encyclopedia
If I am not mistaken, the stock timing is approx. 19* BTDC. If you advance it to say....29* it would run backwards, but I don't know where the sweet spot would be for it to run well backwards.
I have yet to read on this forum or any of the other forums of anyone trying to run a China Girl backwards. Sorry I cannot be of more help to you.

Just running silly ideas in my head, What would happen if you were to install the mag rotor onto the crankshaft backwards and the mag coil up-side-down? Or perhaps some combination of all that? I know that you would have clearance issues between the mag coil and the crankcase as the coil windings are made offset in relation to the center line of the coil frame. Perhaps some careful grinding and spacers would accomplish it? I don't really know....... Just rambling out ideas here.

I believe Manic Mechanic was in the process of making adjustable ignition timing magnets...could look into that as an easy way to find the "sweet spot" needed...?

uniblab · Jul 15, 2012

Al.Fisherman said:
Ummmm this reminds me back when I was in High School, of a 2 cycle car that was built to run backwards...This car had no reverse. In order to go into reverse, you stopped the car, turned the ignition off, and restarted it in the reverse position. I can't for the life of me, remember its name. It was made in Europe somewhere. It was a funny car, someone that I knew, his friend brought it from I think Great Britain. So, Yes, It is possible to run a 2 cycle backwards.

One year later here are the missing details to the above post:

I'm quite sure you're talking about the German made Messerschmitt Kabinenroller (later known as the KR175, KR200 and Tiger). These were one of many "bubble cars" that were very popular in Europe after the war. Both gas and cars were scarce and expensive at that time and people didn't have much money to spend, motorcycles and mopeds ruled the road until these sorts of mini cars came out.

The Messerschmidts used a side opening canopy that looked like something off a fighter plane. Because of this a silly story got started that these were leftover inventory from Messerschmitt war production but this is not true. The car was originally designed by a feller named Fritz Fend and was intended for invalids and war veterans who were missing a leg, the side opening canopy was for ease of egress.

The early ones lacked any method to go backwards and drivers would often carry a cane or stick and push it against the ground which would permit them to "row" the car backwards. Later cars had the reversible ignition system. This arrangement made for 4 gears in either forward or reverse!

Haven't owned one of these but I've had 3 Isetta 300's along with big interest in little cars.

PS The Tiger models were sort of the hot rod version and became such a popular race car that there was an entire class dedicated to them.

Saddletramp1200 · Jul 15, 2012

My neighbor had an Isetta, It was a cool car. I had a Suburu 1200 GL with a 1600 cc motor in it. Loved that little car. I could go about a week on 7 gallons of gas. It had a radio, that's about it. Fond memorys, Thanks (c)

tooljunkie · Jul 15, 2012

i had a merc mark75 direct -reversing outboard motor.
exactly as mentioned above,the distributor would rotate when shifted to reverse,the button on the shifter would start it in reverse.neutral was off.thing was a pig for docking and putting it on a trailer.very difficult for slow maneuvering.
i also have a harley davidson golf cart,starts in reverse.
timing is critical,would need to rekey magnet,and flip the lamination over,i believe trigger would put it in the right place to fire it in time.

time it wrong and it will go through pistons like my dog eats cookies.

2 stroke running in reverse

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