2 stroke reverse snowmobile engine.

[Beeman]

My brother in law has a snowmobile that reverses the engine rotation for reversing. Can anyone explain how that's done? It slows down rpms when you hit the switch, doesn't come to a complete stop but does start back up in the other direction. Does it simply fire on an upward stroke instead of downwards?

[Groundhog]

It is surprising how many engines will run backwards. The engine really doesn't know direction in many cases, just tdc relation. You could adjust ignition timing and make any engine run backwards. Just have to watch out on an engine with an oil pump!

Long ago, we used to try different mini bikes backwards, then have contests to ride them. A honda 50 will run backwards, and a benelli 90 also.

Most big ship engines reverse by shutting down and restarting backwards. This is much easier than having a giant gearbox.

[number1cas]

It flips the timing around aprox 180 degrees, hits the kill switch and then fires it back up without stopping. This is only possible with 2 strokes and the oil injected ones have to have an oil pump and water pump designed to pump forward no matter which direction the engine is turning, most will also default back into forward after a small time period as the water pump will not cool the engine for long while in reverse. It has eliminated the reverse gears and parts in the chaincase, they also require special clutches to allow them to close in reverse. They use compression springs and not torsion ones like normal.

[gearhead1937]

My old man used to tell a story about his old Butaco (maybe mispelled) and a hill climbing incident. About halfway up the hill he was running out of steam so he pulled in the clutch just as the engine was about to die. Little did he know at the moment he pulled in the clutch the motor hit TDC and started running in reverse. He said he reved the you know what out of the engine and dumped the clutch expecting to continue up the hill, you can imagine his suprise will it took off backwards. I know not 6 wheeler related, but a funny story I thought I'd share.

[elwesso]

The old Merc straight 6 outboard marine engines (sometimes referred to as "dockbusters") ran forward and reverse.. The starter had 2 bendix's, so when you would put the shifter in forward or reverse would dictate which gear the starter would engage.. It also had 2 distributors...

[Robinhood02]

My brother in law has a snowmobile that reverses the engine rotation for reversing. Can anyone explain how that's done? It slows down rpms when you hit the switch, doesn't come to a complete stop but does start back up in the other direction. Does it simply fire on an upward stroke instead of downwards?

actually all engines fire while still on the up stroke about 6 to 10 degrees BTDC (before top dead center)
in the snowmobiles it is a computor controled process where it stops the fireing till it sences that the RPM are correct and it is nearly stoped then it fires about 20 degrees BTDC thus being too early it will push the piston down before it reaches TDC and cause it to start turning the wrong way then it immediatly fires at the normal 6 - 10 degrees again but in the oposite direction.
You can do this by accident when you accidently hit the kill switch on a snowmobile and just by luck pull it on at the right time, i think this is how it was invented (note; if it happened to you by accident you instantly realized something was wrong because it ran like crap and nothing happened when you hit the throttle, all you had to do was shut it off and re-start it and all was well)

[mark polinski]

ive got a jlo rockwell 340 that ive put into a golf cart,i was told that all 2 strokes would run backwards but i havnt been able to get this one to do it ,that wopuld be nice to have reverse on it

[6X6]

Reed valve and piston port 2-strokes will run backwards. Rotary valve engines wont (or just barely) (Like Rotax, or R/C nitro engines) Your JLO is a Piston port and it will..... BUT you have to have a starter that will spin it in the opposite direction AND, you need to change the timing so that it fires before not after top dead center when spinning backwards. As it is, if you spun it backwards your ignition would be very retarded and the engine would run just like Robinhood said, like a pile, little power, and backfiring.