1979 YZ250 Super High Idle, Not starting easy

My YZ250 was running pretty high idle so I decided to pull the carb to clean and check the pilot Jet as I figured it was Jetted rich cause the guy I bought it from lived at elevation and rode in the dunes alot.  I found that the Pilot was set to a #70 when the stock should be a #50.  The needle is set on the leanest setting.  I then cleaned the carb put everything back together and now it is super high idle when I start it and then i kill it so I wont blow the motor and then it wont start.  Not sure what the deal is here?  Any help would be appreciated!





Your running super lean, either from an air leak (most likely) or your slide is being held open slightly from a cable misadjustment or idle screw being set to high.

well I made sure that my idle/fuel mix screw and air was adjusted to stock.  1.5 turns out on air and I believe 2 on fuel.  But I did not check my slide after I put the carb back on the bike.  Where else would I have an air leak?  Nothing has changed and it ran high idle before but not this high.  

There is many locations where an air leak can develop. Carb manifold, reed spacer, reed cage, exhaust leak, crankcase seal, etc.. come to mind. A simple leak down tester will show you if this is the case, and will show you where.


Make sure your carb slide is closing completely first. Back the idle screw out completely, and "snap" the throttle shut. It should make a dull sounding "thud" when the slide bottoms out on the carb body, as opposed to a sharp "clack" if the slide contacts the idle screw.


Your throttle cable might even be preventing the slide from closing, if the tension is too tight. This is where you probably should start.

Will do, thank you for the advice!  I will try that and get back to you.  Since it was running relatively good before I assume it is the throttle cable adjusted incorrectly or the slide like you said.  Thank you again, 

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