First post in the forum and looking for some help. We just bought a used Unsion 90 2 stroke my daughter loved it for the first few rides, but now it won't start. Things checked so far-
Compression- 120psi
Spark, yes and new plug.
Carb- cleaned a couple times. not much varnish, but a few pieces of gunk here and there. Fuel coming out the overflow if left overnight, even after cleaning needle and seat. It was jetted rich(previous owner had pipe, which I removed), so top of piston is black. Currently have stock jetting.

At times, the machine wants to run and fires a little, but not enough to run. Is there a chance that carbon built up and won't alllow it to start? Any thoughts on where to check next?

 

The silencers can get plugged with soot. Some have a lil screen that's prone to plugging.
If fuel is comming out, it's flooded. Full throttle till it starts.
Install a on/off valve in the fuel line.

 

Ok, will check that out. I still have the Hetrick pipe that I can put back on also.

Are there transfer ports in the cylinder that would get carboned up also?

 

Nah, not any problems with the transfers gumming up.

 

Ok, so got it to run a little bit by turning on side and pouring gas into the carb. I had put the carb on a similar machine(Xtreme 70) and that machine ran fine. So it appears I am not getting enough gas, but the carb seems ok. Is it the control for the electric choke? I switched the solenoid out with one from the Xtreme, but that didn't seem to help. I thought maybe there wasn't a signal going to the choke to tell to choke. Is there a way to check that?

Removed reeds and there was suction into the motor. Turned it over and had a little oil fire for a few seconds in the crankcase until we put it out.

 

After reading other forums I think I'm ordering a manual choke kit for it.

 

Ok, that didn't work. I have spark, 120 PSI compression, and fuel going to the carb. I'm missing something, please help.....

 

Sorry, fuel going into the cylinder...the spark plug is wet.