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trippcobra

throttle sticking a little bit on my YZ450F???

10 posts in this topic

When I roll off of the throttle, it stays a bit above idle for a second or two. I don't think its in the linkage or actual throttle, is it maybe internal in the carb? any help appreciated. thanks

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That's called a "hanging idle", and it's caused by a lean condition at closed throttle, and/or an air leak.

Check your bike for a shrunk carb isolator (mount sleeve) (one that will no longer clamp down), or any other source of air leaks.

Attempt to adjust the idle mixture to correct the problem per the manual.

Check the float level.

Check the valve clearances. A hanging idle can be caused by tight intake valves. If you find this condition, and any valve requires a shim more than .10mm thinner than the original, you need a valve job.

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That's called a "hanging idle", and it's caused by a lean condition at closed throttle, and/or an air leak.

Check the valve clearances. A hanging idle can be caused by tight intake valves. If you find this condition, and any valve requires a shim more than .10mm thinner than the original, you need a valve job.

by valve job you mean to adjust them?

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No, that would be a valve adjustment. I mean the valves would need to be replaced at that point. You can try to run them longer, but you will most likely find that one or more of the ones that needed the big correction will be ot of spec again after 2 more hours or so.

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No, that would be a valve adjustment. I mean the valves would need to be replaced at that point. You can try to run them longer, but you will most likely find that one or more of the ones that needed the big correction will be ot of spec again after 2 more hours or so.

2 hrs...........i would half to adjust them 3x in a day:excuseme:

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Which means your valves are "HIGH TIME PARTS" and you need to replace them.....

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If either of you two are using u4 or the u4.2, it could be that little crystles are forming on the slide and it just needs to be cleaned!

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The only problem you have is like Gray said. A lean condition. Being that these are new bikes the intake boot is not likely the problem. You should be able to correct it by turning out your fuel screw. If you have to go more than 2 1/2 turns, you need a bigger pilot jet. What gray means by needing to replace the valves is that if the clearances are that far off...tight..... then the valves are already "dished" and a valve job will need to be done. This is very common with the CRF's not the YZ's.

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