Vibration and running issues with bike??? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 17 (permalink) Old 08-24-2011, 12:30 AM Thread Starter
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Question Vibration and running issues with bike???

So I just had my engine torn apart and put back together and now I have some issues I cant figure out. (rebuild was for a broken shift linkage) I reinstalled the engine, added cobra exhaust, pod filters on carbs, rejetted, and coastered the bike. It took some work but I can start the bike and it will idle about 1200 rpm fairly well. Been working and riding on and off for a week now. It drives fine and shifts through the gears with no issues. My issue is that it vibrates like crazy. On a 20 minute ride my butt, hands, and feet were all falling asleep. This is at all speeds and even at idle. One of my carbs has a tendency to backfire through the air filter/carb occasionally after warming up as well. Im not sure if the 2 problems are related or not.

I have checked all mount bolts, intake leaks, removed carbs and checked, etc. Im not sure what I am missing or whats causing the issues. I tried checking my carb sync and it seemed like it was pretty even. Does any one have any ideas what might be causing these problems?
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post #2 of 17 (permalink) Old 08-24-2011, 01:44 AM
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Were the timing chains installed with all marks lined up and at TDC? Could anything have slipped during the installation of the next parts? Were all the pieces put back or replaced correctly in the balance wheel? Sounds like something is rotating out of line or out of sync with the rest of the engine. Just thinkin' ....
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post #3 of 17 (permalink) Old 08-24-2011, 02:22 AM Thread Starter
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Im sure its possible. After reading im kind of leaning towards the balancer not being installed in line with the rotor. My mechanic rebuilt the engine and hes been excellent with everything but he might have messed up. Im just trying to rule anything else out before removing the engine to check AGAIN (4th time)
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post #4 of 17 (permalink) Old 08-24-2011, 03:12 AM
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I agree with bat but, could it be as simple as carbs out of sync? As far as i know (and thats not a whole lot) but the not liking to idle with the vibration could be timing or carbs or both. if it were me i would start with the easy most accessible possibility the carbs, as for the other possibilities ie timing or balance that is a motor pull.

if im wrong one of the others here will chime in.

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with 14,000mi
now 18,000mi
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post #5 of 17 (permalink) Old 08-24-2011, 08:16 AM
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I was thinking Carb sync as well.
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post #6 of 17 (permalink) Old 08-24-2011, 10:36 AM
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You don`t say how old the bike is, so I don`t know if deteriorating balancer dampers are a likelihood.

Gordon

1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

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TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO. Click on link.
https://www.vn750.com/forum/11-vn750-general-discussion/9127-top-ten-items-you-would-suggest-new-owner-do-his-new-ride.html
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post #7 of 17 (permalink) Old 08-24-2011, 10:53 AM
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^X2 he probably should have replaced those too while he was in there.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
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post #8 of 17 (permalink) Old 08-24-2011, 12:18 PM Thread Starter
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The bike is a 91. Im not getting any chunks or pieces in my oil screen or anything but it might by installed wrong. I checked my sync and it seems right on. Ive had vibration issues from out of sync carbs and it seems much worse than that. How hard is it to check the balancers if i pull the engine? is there a large amount of disassemble or fairly easy to see. Im going to double check the carb sync but im almost sure its not that.
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post #9 of 17 (permalink) Old 08-24-2011, 09:47 PM Thread Starter
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So it is def not the carb sync. Checked it again and its right on. All bolts tight and its def coming from motor. How hard is it to check the balancer?
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post #10 of 17 (permalink) Old 08-24-2011, 10:00 PM
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Might be a silly suggestion but what about the engine mounts? I mean if it runs through the gears, revs and idles well, I would think the internal balancer and valve timing should be ok or it wouldn't ride well at all. Just thinking that if a damper in one of your engine mounts is out of place, or a mount is too tight, the engine vibration is now being transferred through the frame to your hands and feet. I have a hunch that this may be your problem. Good luck,
dt
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