Hello all,

I bought a 01 yz250f a few weeks ago and it had took about 10 kicks to start from cold. After you got it warmed up it started and ran well except for some popping on deceleration. I thought that I should try upping the jetting to a 48 and it didn't run well on that.

So after putting back in the stock 45 I cannot get it to run well again and have tremendous bog off the start and after revving the idle takes time to go back down and hangs at high idle levels

Thanks alot and any help will mean alot.

Lean in the first quarter of the throttle. check the pilot jet to make sure its not plugged. Also play around with the air screw: try half a turn in.

I tried that and it helped the idle hunting but not totally. The throttle cables are not hanging up. They go back down very smoothly. That didn't help the bog tho.
Any other thoughts?

sounds like you may have an air leak. make sure that the carb is seated properly in both boots. also check your pilot jet

For the hanging idle try spraying the idle adjustment screw assembly from the adjustment knob all the way to other side of the carb where ity goes into the throttle cable cover. Start the bike up and let it get to operating temperature. Then turn the screw in and our until it turns easier.

A lot of times this is the issue.

Edited by Charlie755, 30 April 2012 - 05:35 PM.

So i checked the boots to make shure no air was leaking in through. Pilot jet is clean. I have been adjusting the fuel mixture screw and it doesn't change it all that much. I lubed the idle screw and it turns freely. Throttle Cables are not bunching and slide to idle very nicely.

I took a video to show the problem:

Edited by joshc6464, 01 May 2012 - 01:13 PM.

Just a update:
I think I might have found the problem.

When I started the work I replaced the stock fuel screw with a Tusk One.
I think that was a big mistake from my further reading on here.
Im going to put the OEM one back in

joshc6464, on 02 May 2012 - 03:46 PM, said:

Yup....tusk screw didn't work on mine either, caused a super rich idle that I couldn't cure until I put the stock screw back in.
RM will give you a refund if you ask and describe the issue....but they deny there is a problem with them.

I threw out the packaging stupidly. I doubt they will give me one w/o it

joshc6464, on 02 May 2012 - 06:51 PM, said:

you don't have to send it back or anything....they will just send you a refund if you explain your situation.

just noticed your bike has brake away levers and bark busters.. mine has the same thing from previous owner.. always wondered why?