Suzuki 2 Strokes

Just tried to start my 750M after restoration. The engine started and ran for a couple of seconds before coming to an abrupt stop. To make a long story short, after removing the SRIS valves I found the left cylinder had at least a cup of oil in the crankcase after sitting for 20 years. The oil was removed and the engine turns over freely. Ater trying another start the engine acted as if the timing was off. It would kick back against the starter and had a slight backfire. It would not start. I checked the timing marks and the timing is correct to the timing marks but the timing marks are as much as 50 deg off from the correct piston positions. The degree of variance is not the same on each cylinder. I know this isn’t good but has anyone seen this before. Any ideas on what might have happened?

Sounds like your left cylinder hydro locked when the others fired. I would think something bent on the crank or the crank spun on the pins when the left locked. Sounds like you will need to open engine to find out.
If you never pulled the cylinders on a 750, it can be an adventure, you will most likely need a puller.
First thing I would check is, pull left side cover and check points cam to starter clutch pin, make sure nothing wrong there then check key that holds starter clutch to crank, check key is not sheared allowing slippage on crank. If piston positions vary to much problem is probably deeper.
Also timing marks are just a rough setting, timing on each cylinder should be set with a dial gauge.

I agree that it's probably the woodruff key inside the starter clutch that sheared. They do that. Fortunately it's an easy fix.

Thanks for the replies to this post! I removed the starter clutch today and the woodruff key had been sheered. Hopefully this is all that needs to be fixed.