YZ450F Idle problem

Hi there. I am sure you guys on here will square me away pronto.

Here is the problem.

I have a 2004 YZ450F. Bought it a month ago.

If I increase the idle, by turning the idle screw, it goes up for a couple of seconds, then drops down to a slow idle again. If I blip the throttle it sits at the higher idle foe about 5 seconds then drops down again.

Any ideas ?

This is a "hanging idle". It's normally a lean condition. Start by checking for obvious air leaks, then get the idle mixture set right. If that doesn't do it, check the valve clearance.

I also would set the fuel screw come out richer,but sometimes if you put the idle a hair too high it hangs.Try lowering the idle after the motor is totally WARMED UP , and then try it.

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