Naildriver Posted January 18, 2009 Share Posted January 18, 2009 History: Bike has been sitting untouched and not prepped for extended storage for about 10-15 years. Just finished a complete breakdown/cleaning/rebuilding of the carburetor. Re-installed the carb and started the engine. Problem: Revs fine and sounds good, but wont immediatly return to idle. If you wait a few seconds, or bump the engine on/off switch quickly, it will return to idle. Throttle cables are not stuck and the breakdown of the carb was extensive. All ports were removed and cleaned thoroughly. Any help with diagnosis/resolution would be greatly appreciated. Naildriver Link to comment Share on other sites More sharing options...
Madison Motorsport Posted January 18, 2009 Share Posted January 18, 2009 Have you replaced the return spring on the carb and checked that it is located properly into the cut-outs? Link to comment Share on other sites More sharing options...
Naildriver Posted January 18, 2009 Author Share Posted January 18, 2009 Have you replaced the return spring on the carb and checked that it is located properly into the cut-outs? 99% sure it's not that. Butterfly valve returns and nothing sticks, but i'll re-check and fiddle with it. Any other causes of the problem? Maybe something internal on the carb? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted January 18, 2009 Moderator Share Posted January 18, 2009 high revs means you need to check the idling system as its letting in too much air!! either pilot screw adjustment or you may have overtightened the rubber inlets causing it to bow (use feeler gauge to check) Link to comment Share on other sites More sharing options...
Naildriver Posted January 18, 2009 Author Share Posted January 18, 2009 high revs means you need to check the idling system as its letting in too much air!! either pilot screw adjustment or you may have overtightened the rubber inlets causing it to bow (use feeler gauge to check) It's not that it revs high and only high. When it starts, idles fine. It's after I throttle up and then release the throttle that it won't immediatly return to normal idle rpm's. If I wait five-ten seconds, or if I quickly toggle the on-off switch, it will then return to normal rpm's. Will the above issues be causing this problem? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 18, 2009 Moderator Share Posted January 18, 2009 It's not that it revs high and only high. When it starts, idles fine. It's after I throttle up and then release the throttle that it won't immediatly return to normal idle rpm's. If I wait five-ten seconds, or if I quickly toggle the on-off switch, it will then return to normal rpm's. Will the above issues be causing this problem? There are only two adjustments that you can make from outside the carb. The idle screw ( Throttle stop screw ) adjusts the speed of the idle. The idle air screw adjusts the idle mixture. This is only at idle and does not effect anything above idle. Here is another method to adjust it. Screw the air screw in and out until you get the highest idle speed. Then lower the idle speed with the idle screw and do it again until you get the best idle. If you can't get it to idle, or rather the idle stays real high then drops off and dies, check for an air leak at the carb manifold. Squirt some gas or starting fluid on the manifold and see if the revs change. If they do, you have a leak. If your valves clearances are too tight, it will also effect the idle. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted January 19, 2009 Moderator Share Posted January 19, 2009 when I rebuilt my xs, it could idle but if you rev it, it would stay up there. I merely adjusted (richened) the pilot mix screw till it stopped doing it!! Link to comment Share on other sites More sharing options...
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