Bike won't stay running

[jon333alaska]

I have a yz 250 that will start with a new plug, run for 15 to 20
seconds and then die. It won't start until I clean the plug or put a new one in, and then 15 to 20 seconds again. Drained the gas put fresh 32:1 mix in with a 4oz octane booster mixed in the 5 gallon can. I am using a br8es plug, new twin air filter. I can't figure it out. Any ideas would be appreciated

 

[E T]

:trying to delete this reply: :bang:

 

[NGE]

It won't start until I clean the plug or put a new one in, and then 15 to 20 seconds again.

sounds like a rich gas mixture most likely.... odd that it would be that out of whack unless you (or the last guy to have it running) changed something? (i.e.- changed jets, took apart the carb and didn't readjust, moved to a considerably higher elevation)

do a search on the site for "jetting" or "carb adjust".. you will get more info than you know what to do with

 

[jon333alaska]

I guess I should have wrote more it idles and revs fine for 15 to 20 seconds then sounds like it is loading up and bogs out. Just took the carb apart and cleaned it put it back on. same deal. Guy at the yamaha shop says it's the crank seal 200 to replace or the cdi or stator 250-350 just for the part