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Discussion Starter · #1 ·
Hi peeps, my bike won't idle well, above 1500 rpm and throughout rev range it runs fine, the carbs have been ultrasonically cleaned, float level checked, balanced, and run carb cleaner in the petrol several times. Still doesn't idle as it should. Replaced ignition coils, leads, and pickup coils, compression fine. Starts and seems to be charging ok. Anyone had this problem and found a cure? Any help most welcome.
 

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Discussion Starter · #3 ·
Thanks for the reply Dodsfall, the exhaust is a Motad 4 into 1 but it was doing this before I put it on. I''ll check valve clearances asap, hope this is the problem, it's really pissing me off after weeks of trying.
 

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I'd be thinking valve adjustment at this point. You could perhaps strengthen a decision to check/adjust them by running a quick compression and/or leakdown test on all four cylinders.

Valves out of adjustment, a burned valve, valve problems don't "go away" at higher rpm's but they get hidden better by the higher power output of the other cylinders.

You could rule OUT a lean misfire by adding faux fuel (starter fluid) at idle to ensure additional fuel doesn't "clean up" the misfire. Ditto for vacuum leaks, spraying AROUND the intake manifold, etc. to see if rpm's increase anywhere. Suggest you use brake cleaner, not starting fluid for that as it's too damn flammable.
 

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I've had this problem before, my best guess is the carbs would need to be synchronized. meaning one throttle or slide could be closed while the other would be open.
 
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