help 81 rm125 starts but won't run

[rotaryconcepts]

I'm not a total moron but I can't firgure out this problem.

I was riding my old 81 rm125 last spring and i quit running.
Turns freely, has compression, has spark, is getting gas.
Here's what it does...
Starts on first or second kick, runs normal for 5-15 seconds, won't restart. plug wet as can be. Clean the plug does the same thing over again. I can't firgure it out.
Any ideas?

Thanks
Joe

 

[nickyd]

when you clean the plug it fires right up?

how does it sound when it dies (does it scream? or go BAWaaaaaaaaaaa)

 

[rotaryconcepts]

when you clean the plug it fires right up?

how does it sound when it dies (does it scream? or go BAWaaaaaaaaaaa)

Yes after you dry off the plug it runs again for 5-15 secs.

I don't know if I would say screams, it runs like normal with the choke on and blipping the throttle, but then it dies like i hit the kill switch.

 

[SirHilton17]

My old 1980 YZ 125 did that exact thing when the stators went out..
But before jumping to a conclusion like that try somthing as simple as a new plug, and try cleaning the carb.
Could you have mixed your gas diferent that usual,diferent type of premix oil?

 

[rotaryconcepts]

It started doing this during a normal ride last spring, just puttered out doing this ever since.

I've never mixed gas exactly the same, it's always somewhere between 20 and 25 to 1. 1981 manual reccomends 20:1 with i think 94 or 95 octane, all we have here is 93. I ran race gas in it once (110) and I couldn't tell a difference.

I had a stater go bad before and replaced it. when the old one went bad there was no spark at all, seems to be sparking everytime now.

Might it be possible that one of the ignition componets is working intermitenttly? I've checked for spark right after it dies and it works fine though.

I was too busy to mess with the bike all summer, now I'm dying to ride her.

Thanks for the help guys.
Joe