[2-stroke!]

bought a yz125 1987. it runs fine until it warms up then it dies. I built the whole top end new gaskets. adjusted the power valves. reeds are good. packing in the exhaust in silencer is good. what else could it be??

 

[jaguar]

easy answer is the crank seals. They need to be replaced every 10 years or so. Gasoline with alcohol content can make them last less than 1 year. Old seals aren't made to handle the drying effect of alcohol. Be aware.