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1981 XR80 Idle Gone Crazy!

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Hey guys I picked up a old 1981 XR80 for a hundred bucks got it home cleaned carb, new 35 pilot, fixed the clutch issues got it running and took it for a ride everything works, has good power last owner had the top end done last year. Now the problems I cant adjust the carb to get this thing to idle properly!! I sprayed around with carb cleaner while running doesn't appear to have any leaks. I checked the throttle cable seems fine? My idle is VERY fast. The idle screw seems to have very little control of doing anything, the air screw is half a turn out and when I put it 1/4 turn out the idle slowly comes down and the bike dies. Any suggestions on getting this old thumper to idle again!! Thanks!  Also should note I am getting quite a bit of smoke when riding it.

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Is your carb slide going all the way down?  Are you hearing the "plunk" when you let off when not running?   If not loosen up the throttle cable a bunch.  If that doesn't get it to work you might have a kink/routing issue somewhere.  Not a mini expert but 1/2 turn on an air screw seems low so smoke may be a result of bad mixture when you open it up all the way-way too much gas, not enough air.   Good Luck.

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The intake part between the carb and head is kinda fagile on the XRs, and the rubber can leak or the metal crack. I had a few bikes that did that and caused a high idle that you couldn't tune out.

 

Wrap some duct tape around it as a test.

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Hey guys I picked up a old 1981 XR80 for a hundred bucks got it home cleaned carb, new 35 pilot, fixed the clutch issues got it running and took it for a ride everything works, has good power last owner had the top end done last year. Now the problems I cant adjust the carb to get this thing to idle properly!! I sprayed around with carb cleaner while running doesn't appear to have any leaks. I checked the throttle cable seems fine? My idle is VERY fast. The idle screw seems to have very little control of doing anything, the air screw is half a turn out and when I put it 1/4 turn out the idle slowly comes down and the bike dies. Any suggestions on getting this old thumper to idle again!! Thanks!  Also should note I am getting quite a bit of smoke when riding it.

 

  Would be worth a look at the jet needle and needle jet,(also called the needle and nozzle) in the carb.Pull the slide and needle from the carb and look with a magnifyiny glass to see if the nozzle has worn oval.

 If it has then the low speed control of fuel into the engine has been compromised.The air screw should be set at 1 1/2 turns out and if you need to turn it in to 1/2 to 1/4 you are attempting to control engine speed by the air screw only,and you will get the symtoms you describe. 

  Your engine is probably running very rich at low(idle) engine speeds ,resulting in the smoke.

 Often when you get a older bike it is wise to get a complete carb kit,many include.needle,nozzle,MJ,PJ and needle and seat and a gasket ...can save you a headacke or two

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