2GM20 Smoking on StartUp

[a64pilot]

Ever seen a Harley Davidson Golf Cart?
Silly thing was a two cylinder, two stroke engine with two sets of points, starter would spin backwards and it would fire off the other set of points and run backwards whenever you needed reverse.
Although rare but almost any engine can be made to run backwards, but usually very badly cause the timing is way off.
Nothing else I can think of would account for your symptoms, I would check my fuel injection timing though, I'd be surprised if it wasn't too advanced

[Cadence]

Originally Posted by a64pilot

Ever seen a Harley Davidson Golf Cart?
Silly thing was a two cylinder, two stroke engine with two sets of points, starter would spin backwards and it would fire off the other set of points and run backwards whenever you needed reverse.
Although rare but almost any engine can be made to run backwards, but usually very badly cause the timing is way off.
Nothing else I can think of would account for your symptoms, I would check my fuel injection timing though, I'd be surprised if it wasn't too advanced

Harley made a golf cart that was made to do that. Start it in one direction for forward kill it start it in the other direction for reverse. I recall a tug boat that reversing it was shutting down and manually throwing a lever to change cams.
Not very relevant to the OP. I think as said above, he just killed the starter at close to the top of a compression stroke and it fired but went down before getting over the top. It might even be good? It might say he has good compression.

[topmast]

Killed a perfectly good engine once by prematurely releasing the stop cable .Engine restarted in reverse and sucked back enough water to bend a couple of rods. Many $000's later the bruises on my butt are fading

[bailsout]

My 2qm15 was always very difficult to start after a 24 hour period. I knew it was about to start when it would start to run backward and I would quickly stop it. Lots of smoke from the air filter. The problem was timing, but not valve timing. It was the timing of the fuel distributor/injection pump that is controlled by shims. I don't know if the 2gm20 also uses shims. After reshimming mine the engine now starts immediately!

[merrytimer]

With 5 of you guys talking about the engine running backwards I am now a believer. It really sounds like this is what happened. I will also look into the timing & fuel injection suggestions. Many thanks!

[SV Bacchus]

Had a friend ask me to help him push start his Mercedes Benz due to a low battery; one of the older model Diesel engines. I was pushing and he accidentally put the vehicle in reverse. When he "popped the clutch" the damn thing started and ran backwards!

I think they have safeguards against that sort of thing now but yes, it can happen.

[Cadence]

Originally Posted by merrytimer

With 5 of you guys talking about the engine running backwards I am now a believer. It really sounds like this is what happened. I will also look into the timing & fuel injection suggestions. Many thanks!

I would suggest seeing if it happens again before doing anything, it could have been happenstance. If she it hard starting I might approach it from that aspect.