Bike surges RPM'S when idles - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 4 (permalink) Old 04-08-2019, 08:51 AM Thread Starter
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Bike surges RPM'S when idles

The 86 I just fixed up and sold is now having issues. I rode it almost 50 miles and didn't experience any issues but the new owner says when sitting and idling it's will surge up to 3k and back down on it's own. Carb boots are fine, no cracking. He pulled the carbs already and said everything looked good there. Diaphragms and slides look good.

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post #2 of 4 (permalink) Old 04-08-2019, 10:38 AM
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The 86 I just fixed up and sold is now having issues. I rode it almost 50 miles and didn't experience any issues but the new owner says when sitting and idling it's will surge up to 3k and back down on it's own. Carb boots are fine, no cracking. He pulled the carbs already and said everything looked good there. Diaphragms and slides look good.
Might try some seafoam gas additive. might be some gunk in the jets. also, check for vacuum leaks (spray carb cleaner around questionable areas). i had issues and even though the carb boots weren't cracked, they have alignment marks that need to be lined up when you put them on. once i lined up the carb boot marks, my bike ran way better.

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post #3 of 4 (permalink) Old 04-08-2019, 05:15 PM
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Almost has to be an air leak.


Just being rich wouldn't rev up without extra air.

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post #4 of 4 (permalink) Old 04-10-2019, 12:38 PM
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Check the coasting enrichener diaphragms. Mine did something similar many years ago. I found both the diaphragms melted, probably by ethanol. Part number 43028 in this diagram. https://www.cheapcycleparts.com/oemp...rburetor-parts

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