03 YZ250F idle problem

OK...dont get mad...I searched the forum and read all carb/idle problems. None seem to be exactly what I'm experiencing?

1. Cranks 2nd or 3rd kick...no problem

2. Once warm the bike idles as if the choke is on...very high.

3. If you come to a stop the bike takes 8 to 10 seconds to idle down to normal idle and sometimes it will not come down unless you clutch the bike and then it always drops to a normal idle.

4. If you barely touch the thottle it goes straight back to high idle.

5. It seems to be running lean.....heats up very quickly...more than normal when setting for a few seconds at idle. Pops alot on deceleration at any speed or any gear.

6. Although I havent riden it very much since the high idle started it runs great through out all the throttle positions except for 0 throttle were it is high idle.


No changes have been made to carb/idle settings.

No major wrecks or changes to bike

Only changes are oil/oil filter and air filter maintenance

Check'd value clearance 3 weeks ago...all within specs

Check'd air boot and all clamps between carb/air filter and carb/head. No cracks or tears found.

Check'd decompression plug. Not broken or no cracks.

I'm do not know what else to check? I'm going to take it to my repair guy at end of week. He is very busy and I probably will be without a bike for several weeks. If you have an ideals about what to check or what the symptoms may be please let me know. Thanks in advance!

Do you start it with the choke? If yes, when the choke is pushed back in does it idle down? If no, check your choke assembly. As well check your hot start for proper adjustment. You could always try cleaning out your carb

Yes I start with the choke. The choke changes the tone of the high idle but does not affect how the bike runs unless it is fully warm and then it runs rough.

I have check'd the hot start and it seems to be adjusted ok? Actually I never really use it. Bike always starts great wthout it.

I have not taken the carb apart and clean'd yet. I'm going to recheck my intake value clearances....I found one post that suggested if the intake values become tight it can make the bike run lean at idle? If the values are still in spec I guess clean'n the carb is something I will try next....thx

Try opening the fuel screw in 1/4 turn increments. Keep track so you can put it back to where you were.

You say you inspected the intake tract for leaks, but did you squirt starting fluid around the joints while the bike was running? If it speeds up, you've found a leak.

Also, clean out the passages in the pilot circuit using carb cleaner and compressed air. Take out the fuel screw (don't lose the spring, washer and o-ring) and remove the pilot jet and pilot air jet. Squirt carb cleaner then compressed air through the passages and re-install jets/fuel screw (be sure and count how many turns it takes to seat the fuel screw before you take it out, so you can put it back where you started).

Make sure the hot start isn't leaking air. It has a funky o-ring that can get torn, and the hot start cap can strip or get cross-threaded easily.

Just some thoughts to try.

Also make sure your throttle cables are not frayed or hanging up.

It sounds like you have an air leak or a sticky throttle. I would check your hot start plunger and make sure it is not sticking. Remove, clean and lightly lube the hot start plunger. Loosen all your intake hose clamps readjust carb. and retighten. Remove, clean and lube throttle cable and throttler tube housing. I would also take the carb. off and clean all passages with compressed air and make sure your slide moves freely.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now