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YZ80 float setting/Jetting problems

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Recently purchased this bike and it runs good with exception to a low end stumble.

Problems noticed when I first pruchased it:

1) Sporatic idle (idle speed would go up and down)

2) Ran choppy going thru 1/4 to 1/2 throttle

3) Fuel dripping from float bowl vent tube after sitting for 10 - 15 minutes. (engine off)

Note: Performs well at high RPM w/ plenty of power.

Adjustments made since:

1) Thoroughly cleaned the carb ( but it appeared clean prior)

2) Adjusted the Needle Valve to top clip setting ( lowered the valve to the max)

3) Adjusted the float tab upward (note I don't know the spec, so i played it by ear)

Perfomance after the above adjustments:

1) Not near as choppy at low RPM, but still has a slight stumble at 1/4 throttle as I casually cycle thru each gear.

2) Idle is much more stable

3) Fuel still drips from float bowl vent tube after sitting 10 min ( but appears to be less before)

4) Still performs well at high RPM

Question:

Based on the above info, how can I remedy the stumble at low RPM and stop the fuel drippage ?

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I replaced the need valve.

Replacing the need valve stopped the fuel drippage, and corrected the low stumble.

It now idles perfect and runs great low RPM.

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