Runs, Stalls then backfires

[jlkass]

I have recently replaced my CDI on my 83 RM250 (no spark). I tried starting it (with the old plug still in it) and flooded it. I drained the excess fuel out, put new plug in it and fired it up. It was running ok for a minute or so - revved up ok, then it just died (like no fuel). After that, every few kicks I would get a backfire out the exhaust?? I have checked the flywheel - thats ok. There are no cracks in the intake boot, reeds are good and I have pulled the carby down and cleaned it.

When I pull the plug out, it is covered in fuel. Pretty sure floats are ok - the bike ran fine until the CDI **** itself.

The only other thing I changed was my fuel mix from 40:1 to 25:1. Could this be making a difference?

Any ideas???

 

[Dockillemall]

Backfire is back through the intake. Afterfire is out the exhaust. Backfire is lean. Afterfire is rich. Looks like you have a rich condition, maybe float is stuck open.

 

[cr_kid]

Your timming is to retarted, advance it slightly. You should also find that the engine wont run as hot as it used to.