Alright, so here is the story.
I bought a 1979 Yamaha QT50 off of craigslist. At the time it was running well and started easily. Since then I've put about 50 miles on it. As I've ridden it its become harder and harder to get it to start, to the point where it will no longer start.
I've done some diagnosing. I started with the spark plug, the spark was weak and intermittent so I replaced the plug, and when that didn't help I replaced the coil. I now have a strong clean blue spark.
After that failed to fix it I tore down and cleaned out the carb. I went into all of the jets with carb cleaner and disassembled it. It wasn't too bad, but I cleaned out what varnish there was.
Again, didn't fix it. I opened up the cylinder and found both the cylinder wall and piston badly scored. (I'm guessing from when the oil pump died, I've been running it on 32:1 Amsoil 2 stroke with 91 octane Ethanol free) Assuming this was the issue I again replaced both, and again, no fix, although I now have about 90psi of compression where before it was in the low 30s.
I've checked the reeds and they appear to be in good shape and look like they've been replaced. The bike also isn't starting with the help of starter fluid, so I'm ruling out a fuel issue.
The only thing left I can think of is that the timing is somehow off, but I don't know how to test that theory, or how you would correct that.
Anyone here have any ideas?