I was riding my yfz the other day and i noticed when i first hit the gas it would bog down really bad and then it would pick back up with full power all of the sudden. It only does this once it gets warmed up. I thought it might be trash in the carb so i cleaned the carburetor out. Then i took the plug out and the plug seemed fine so i put it back in. I've even drained the gas and put new in it and it still does it. Any ideas? Thanks

 

Only does it after it's warmed up makes me think valve clearance... (anyone else?) Otherwise, it sounds like you need to check the pilot jet... may need to try a different one...

 

go on ebay, or local dealership and buy a MSR fuel air mixture adjustment screw. there like $20.00 and it should fix your problem. Most dealerships don't even set the carb air fuel mixture when they assemble the bikes. You may already have this so try adjusting it two turns out, go 1/2 turn from there until it starts running bad, and go back to the last turn. Might be your problem.

 

i dont think its the fuel air mixture. it just started doing this all of the sudden.

 

I agree with Hebs. It sounds like a valve clearence problem.

 

well i changed the plug today just for safe measure and that seemed to fix it. now the battery is dead.

 

If it comes back, its probably your throttle position sensor. Bypass it.

 

how would i do this? also where is it located at?

 

I'll have to ask my buddy, it was his that it happened to.

 

MY YFZ DID THIS AS MY BUDDY SAID BEFORE......... YOU HAVE TO BY BYPASS THE WIRE THAT LEADS TO YOUR THUMB THROTTLE ON THE BOTTOM I'LL GO OUT TONIGHT AND LOOK AT THE COLORS OF THE WIRES BUT YOU JUST HAVE TO CONNECT THEM DIRECT AND YOU'LL BE GOLDEN I HAVE AN O7 AND IT DID THIS RIGHT AWAY....... AND I DID ALL THE THINGS YOU DID AND NEVER CHANGED HAVEN'T HAD A PROBLEM SINCE.........I'LLL LET YOU KNOW.............