i have a yamaha yz-125. last time i rode it it ran fine until i decided to make a full throttle run...ok so i'm in 6th gear and about to top out the bike when the engine cuts.Soi try to start it and it wont start up. Today since i had time, i try to start the bike with no luck.I check the spark plug and thats fine its not drenched in gas, i check for a spark and its there but it does not start. Another thing the carb is leaking a lot of gas if i leave the gas valve on . I know this thread is more about street, but any help is appreciated thanks.

 

perhaps, it's just better to practice safe sex

 

Do you ride it often? Only thing I can think of is if it sits for extended periods the gas could gunk up the carb and the float valve could get stuck open. This shouldn't leak gas into the combustion chamber while the engine isn't running, but it would cause the A/F mixture to be overly rich and bog out the engine.