Rhythmic clunking sound - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 13 (permalink) Old 05-10-2007, 11:58 AM Thread Starter
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Rhythmic clunking sound

I have a mystery noise for the wrenchers here to diagnose. When I start the bike I hear a clunking sound very similar to the sound of a gear change. It is just a clunk..clunk..clunk about 3 times a second, and it does not increase in frequency when you roll on the throttle. It is not very loud. I can hear it when I'm riding, but only when I roll off the throttle. It seems to decrease as the bike warms up. It is not really a brand new noise. I've been hearing it for some time now, maybe since I've owned it. Is this a normal noise, or something I should get checked out.

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post #2 of 13 (permalink) Old 05-10-2007, 12:24 PM
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MIght be the ACCT, cam noise is loud.

Chad Falstad "Hawk"
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post #3 of 13 (permalink) Old 05-10-2007, 02:15 PM
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If it does not increase when you roll on the throttle, it is probably not engine related. Had it increased freq with an RPS increase, then I would suspect the ACCTs. Can you localize where the noise is coming from?

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post #4 of 13 (permalink) Old 05-11-2007, 10:22 AM Thread Starter
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That was my thought too. Other than from the engine area I can't really narrow it down. I am doing some other work on the bike this weekend and I will listen around it and try to tell more specifically where it ias the loudest. Is there something (oil pump, water pump, etc) that operates at a steady rate no matter how fast the engine is running? This is not anything that is affecting it's performance (so far). My bike is a 95, but the mileage is low. It had 2800 on it when I bought it last May. It is right around 10000 now.
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post #5 of 13 (permalink) Old 05-11-2007, 12:42 PM
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The fact that it doesn't increase speed with the engine speed has really got me baffled. The only electric motor I can think of is the fan motor, other than the starter. Drawing blanks here.

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post #6 of 13 (permalink) Old 05-11-2007, 01:57 PM
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You might be able to isolate the sound with a mechanics stetascope. About $10 at you parts store. I used to use a piece of broom handle. Place your ear on one end of the wood and move the other end over the engine. The sound will usually be louder close to its origin. Try several different angles to find the center location for the sound. You must be sure of solid contact between the wood and you engine for correct sound conduction. I agree that it is not an internal engine part if the sound does not increase in frequency with the engine RPM's. Fan motor is one possibility also check out electricl relays.

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post #7 of 13 (permalink) Old 05-11-2007, 02:02 PM
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You mentioned that it seems to decrease as the bike warms up.. which makes me wonder if it's the coffee grinder sound related to the clutch.
What type of oil are you using?
A quick test for you.. when you start up the bike and hear the sound does it go away if you squeeze the clutch lever several times?

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post #8 of 13 (permalink) Old 05-11-2007, 02:48 PM Thread Starter
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I use Shell Rotella T 15W-40. I will try what you suggest with the clutch. The little clunk when you shift is the closest thing to the sound I hear, so it makes sense that it may be a clutch thing. I don't think I would describe as a coffee grinder noise though. It is much more like if you lightly tap the side of your thumb on your desk at the rate of 3 or 4 taps per second.
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post #9 of 13 (permalink) Old 05-20-2007, 09:11 PM
 
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Hi Joem,

I have the same problem..! I'm riding a 1995 vn750, great bike, but this problem started a few months ago, after using a synthetic oil instead of the SE, SF or SG API service type oil they specify. These bikes have an oil immersed clutch.

I tried tightening the timing chains, but these are supoposed to adjust automatically. I have also listened with the screwdriver and the scope, but very difficult to detect.


I think I'll take it to my mechanic soon, maybe tomorrow, and see what he says, but I suspect either clutch related or timing chain related....

I will get back to you soon...
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post #10 of 13 (permalink) Old 05-20-2007, 11:06 PM
 
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"Light tap of your thumb on the side of your desk"......You might want to check for a simple exhaust leak. That is exactly how I would describe the sound mine made when the Exhaust nuts came loose.
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