back poping on down shifts - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 4 (permalink) Old 08-21-2009, 08:07 AM Thread Starter
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back poping on down shifts

I just bought this 750 vulcan and it is back poping when i down shift it does it worst when its cold. any ideas about this problem
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post #2 of 4 (permalink) Old 08-21-2009, 08:15 AM
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sounds like its sucking air from somewhere.
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post #3 of 4 (permalink) Old 08-21-2009, 10:30 AM
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The 750 is kind of a popping machine to begin with. The reed valves on these models are supposed to introduce unburned vapors back into the system before they get into the exhaust and are expelled, but in a short time, they begin to cause the popping. Most of us have either marbled or coastered our bikes to relieve the popping. The marble is the easiest. Get two marbles, regular size, and pull the clamp and hose off of each reed valve, insert the marble into the hose, push it in far enough to put the hose back on the reed valve and re-clamp it on. Do it on both sides. Then ride and see if it fixes the problem. You might have to adjust your idle air/fuel mix screws out to around 2.5 turns to get it to optimum levels. I've never touched my idle mix screws and the marbling alone did the trick, however, the lead caps were gone off my air mix screws so they may have been adjusted by the PO. You can find photos of different parts of this procedure in the gallery. Good luck!

Kyle, TX member #707 VROC#19556
2002 VN1500 Classic
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post #4 of 4 (permalink) Old 08-21-2009, 10:42 PM
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I actually like the sound. Doesn't mean anything's wrong with your bike, that's just how it's made. Some people dislike it enough to mod their exhaust system and make it sound sweeter to them. Some just live with it and some, like me, think it sounds rather distinctive to my baby.


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Pirelli MT66 Tires: 110 front / 150 rear
Splines lubed when tires installed at 10,650 miles
Splines lubed again at 14,400 with stubby valve stem install

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