yz250f dilemma- what could it be?

[schmanman]

I'm asking this question for a buddy of mine-

he took off the head, and adjusted the valves, and put everything back together. it runs like a champ, with the choke on, but when you turn the choke off it pops, misses, and backfires. It also doesn't idle, even with the choke on. you have to give it gas to stay running at low rpms.

he has cleaned the carb two or three times, and blown out all the jets. could the pilot circuit be clogged? how would you go about cleaning that?

thanks for all the help guys!

-Alex

 

[robwbright]

http://www.thumperfaq.com/jetting.htm

The pilot will cause EXACTLY what you are describing. I had the same problem last fall. There was a tiny piece of dirt I had missed.

 

[_JOE_]

Also double check the cam timing an valve clearance.

 

[schmanman]

alright thanks, I'll let him know. :cool:
I told him to go clean out the pilot jet with a piece of wire or just to go buy a new jet.

 

[IndyMX]

Don't clean jets with wire.. Use compressed air.

 

[sharky243]

There is a removable plate on the carb slide, make sure it is not upside down. I made that same mistake and the bike did exactly what you are discribeing. After I put the plate back on properly, the bike ran perfect.

 

[Tdoorn199]

yah definitaly dont use a peice of wire that could scar the jet