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Hi I am new to the site and this is my first posting I have a CRF150f that I haven't had for to long. It's a 2003 and in really great shape hardly ridden. I have been having this contant problem and it's driving me and my dad crazy as we can't figure it out. The first day I took it out the bike ran great all day until near the end of riding I noticed the revs where alittle high and then I rode back to the truck and stopped and got off the bike it was idling really high just sitting there. It almost seemed like the throttle was sticking and we tried playing around with the connection and checked the cable and it looks in great shape and can't see no bends or breaks or anything with it. Next day we went to start it was still reving high. so I warmed it up abit and tried to get the choke off but it would just stall with the coke off unless we kept on the throttle.

We had never had the carb apart yet on this bike since I got it so we took it apart and cleaned it out and yeah it was a tad dirty inside and in the jets so we cleaned it all out good and put it back on and now it starts great and will stay running no problem once warm as yes these bikes of this kind are very cold blooded as my brother has a ttr125 and it's the same. So that part is fixed but now.

The same problem stil exsist which more indepth of it is when I am riding the bike runs great and idles great except when I am riding slow or in a low gear like 1 or 2nd then it wants to rev to high or if I stop and sit there with it running it revs way to high....The odd time it may go down for a sec but still stays high but once I take off and get going the the revs seem good. We have adjusted the idle screw and what not but thats not it either. When you first start it when warming it up revs nice and low but once I move the choke to from on to half way or off if revs high as well then. Other than that any time riding or going fast in a high gear it runs great....... Any ideas?

Pull the plug and see what it looks like, I'm guessing lean.

I have the same exact problem with mine. Except mines a 2004 and it kinda started happening after we cleaned our carb. Now, it seems we cant fix it and im hoping theres a solution on this post.

You boys need to check your fuel screw.

Make sure all the parts are there and in good condition. No hard/dry/cracking in the o-ring.

Check for correct assembly order.


Your symptoms indicate you are lean near the pilot/idle circuit. You either have an air leak or lean fuel screw setting.

I have an 06 and have had the same issues. I drained the gas from the float and gave it new gas and now it will actually idle.
However, I am still having the same high rev issue! I noticed that if the throttle cable is bumped, or moved, thats when the high rev issue comes up. Wiggle your throttle cable when you first warm up the bike...does it do the high rev thing? I am at a loss as what to do now.

Every little honda we've owned ends up with a plugged carb every few weeks if you don't ride them regularly. Usually the high speed jet. They end up idling horribly. It's good to have an air hose available when you clean the carb. Blow air through every orfice and hole that you can find. Carefully remove the jets and Use a fine strand of wire to carefully clean the little holes in the jets.

But you also need the power up kit if you haven't already done it and the adjustable fuel screw. Getting the old fuel screw out is a bugger without the special d shaped tool. Just put this kit in today and the bike runs really nice now. Just do what the instructions tell you to do with regard to setting the fuel screw.

Personally I would do what 124 said re mixture screw.
If you have fast idle which can't be changed by the idle speed screw you MUST have an air leak somewhere.
Whether it is at the boot, mixture screw etc that you will have to determine.

If touching the cable makes it idle up there is not enough slack or it is binding inner to outer. When was the last time the cable was lubed?

Simple faults that can take a while to work out for sure.

Let us know how you all go.

At least the bikes have a choke plate and not a plunger so it should be simpler.

Running into all the same issues you guys are
Idle is high
running lean
pipes getting red and hot fast


Solutions:
pulled the carb, cleaned, rejetted my pilot circuit,
compression and leakdown on the engine to check for leaks there
also checked anything for intake or exhaust

Still idles high but running a little more rich... any other suggestions for the idle besides the idle adjuster??

Thanks
Eryn

Don't believe I saw anyone mention whether they have rejetted from the factory 'way too lean' settings. Check this out, see where you are with relation to the indicated recommendations, and go from there.
http://www.crfsonly.com/forum/viewtopic.php?t=13787
O.D.