Knocking noise from drivetrain only when it's hot - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 6 (permalink) Old 05-19-2011, 08:03 PM Thread Starter
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Knocking noise from drivetrain only when it's hot

On the way back from the Ozarks last weekend blasting down I30 at 70-75mph and the wife says she hears a squeaking noise over 72mph that goes away under that speed. We decide to switch bikes for the rest of the way home. I never hear the noise again for the rest of the ride.

When we get home it is pretty warm outside so we park the bikes on the street while we go inside for a cool drink and strip off our riding gear. After around 15 min or so I go outside and start her bike up to move it into the garage, drop it into first and move forward.

Immediately I hear a knocking noise that I can even feel slightly in the seat of my pants. Length of driveway is about 25-30ft and it knocks the whole way up. Last time I heard a sound like that was when I knocked a tooth off the first gear in my '66 Mustang that didn't have synchromesh on first.

I feel the final drive unit and it is pretty warm to the touch, but no hotter than the one on mine. PO said he did spline lube too. It was pretty late so I just finished putting the bikes away and cleaned up for bed.

Next day I rolled the bike around in the garage (in neutral) and no knocking sound. Open the final drive and it is full of oil. Changed the oil anyway, no sign of metal filings in oil. Our driveway is sloped so I coasted it down the hill still in neutral and on a good ways down the street and still no knocking. Started the bike and went for a 15min ride; no knocking. And it never made the squeaking sound again either. Very strange this is.

Wife rode the bike to work the next day (18 miles one way) and still no knocking. Went out for another ride together for around an hour; no noise, no problems. Had bikes parked on the street again for a few minutes while we moved the cars out the garage before putting them away. Jump on her bike, start it up and head for the garage...it's back knock, knock, knock.

If it was a busted tooth on a gear I'd think it would knock all the time and not just when it's hot. I can't be sure where the noise is coming from exactly because it's not that loud and the bike has to be rolling (and hot) to get it to happen.

Anyone got any ideas what I have going on here?

I figure I'll need to do a spline lube type tear down (already did that on mine) but I'm really not sure what to look for at this point.

Is there any possibility it could be a rear brake problem instead?

HIS - 2006 - Purchased with 1600 miles

Spline Lube, LED 3rd Brake Light in Sissy Bar, LED Brake Light Strobes, F&S Luggage Rack, F&S Engine Guard, F&S Extended Sissy Bar, Faria Voltmeter/VDO cup, 12v outlet, HF bulb


HERS - 2003 - Purchased with 4500 miles

Spline Lube,LED 3rd Brake Light in Sissy Bar, LED Brake Light Strobes, F&S Luggage Rack
F&S windshield, F&S Extended Sissy Bar, Faria Voltmeter/VDO Cup, HF bulb
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post #2 of 6 (permalink) Old 05-20-2011, 05:18 PM
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I don't think everyone is being a jerk and just not answering your problem.........I just think that we are all as puzzled as you are as to what the problem could be??????? My question is when it is making the noise.....you said the bike has to be hot.....like running temp. Now when it is making the noise "HOT" that is with the engine running.......while moving with the engine hot.....what happens if you put it in Neutral while moving at a decent speed and kill the engine......and now your just coasting........Is the noise still there......because at this point the bike is hot....but only the trans beyond the clutch ...the driveline and rear gears are moving....along with rear drum brake poss. being and issue.... I am truly stumped!!!
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post #3 of 6 (permalink) Old 05-20-2011, 11:53 PM
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X2 to Brets remarks. In 3 years I have never heard another set of symptoms like this.
I will be following this thread with interest to see what the problem really is. Good luck.

Gordon

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

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post #4 of 6 (permalink) Old 05-22-2011, 11:51 PM Thread Starter
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Ya know a weekend gets to effing busy when you don't get to ride even though the weather would've been more than cooperative.

Brett, I'm more than puzzled on this one too. When this happens it always after a ride long onough for the bike to be totally warmed up including the rear end. It has always happend when I am putting the bikes away after they have been sitting for a few after the ride has taken place and when I am going uphill into my garage. That being said it the knocking starts before I am on the hill; basically the instant I start moving forward.

I have not stopped and decided to take it down the street a ways and then pull in the clutch as you suggested and kill the engine. I have not had the time to even think about a tear down.

Does anyone think it is OK to keep riding before a tear down? I'd like to try Brett's suggestion, especially because of the conditions that must be in place before any symptoms occur.

My old mustang would knock whether it was hot or cold every time you were in first. Maybe the wife uses the rear brake in excess, but I don't think so cuz she rides pretty good. Maybe the PO's wife used the rear brake alot, I don't know.

I just hate to tear it down all the way if not necessary. I know when I did the spline lube on my bike I never even thought of looking at the rear brake shoes since it only had 1600 on it when I got it. Maybe the PO of the wife's bike never looked at them when he did the spline lube and they are shot with only 5k on the clock.

Does anyone dispute my thought that it can't be a broken gear cuz it would happen all the time, hot or cold?

HIS - 2006 - Purchased with 1600 miles

Spline Lube, LED 3rd Brake Light in Sissy Bar, LED Brake Light Strobes, F&S Luggage Rack, F&S Engine Guard, F&S Extended Sissy Bar, Faria Voltmeter/VDO cup, 12v outlet, HF bulb


HERS - 2003 - Purchased with 4500 miles

Spline Lube,LED 3rd Brake Light in Sissy Bar, LED Brake Light Strobes, F&S Luggage Rack
F&S windshield, F&S Extended Sissy Bar, Faria Voltmeter/VDO Cup, HF bulb

Last edited by mistereman1; 05-22-2011 at 11:53 PM. Reason: typo
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post #5 of 6 (permalink) Old 05-23-2011, 01:18 PM
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Just some thoughts....

It would have to be a pretty good thump for you to feel in through the seat.
So I was thinking loose engine or frame mounts. Something that expands enough when hot to let it bounce around.

Oil.. is it heavy enough. Is it draining off of everything and loosing prime and when you start it, is the Oil Pump having a problem picking the oil back up.

Lastly a sticky valve that is being tapped by the piston. Not stuck just not sliding back in as fast as it should because all the oil has drained off of it.


Quote:
Originally Posted by mistereman1 View Post
. After around 15 min or so I go outside and start her bike up to move it into the garage, drop it into first and move forward.

Immediately I hear a knocking noise that I can even feel slightly in the seat of my pants. Length of driveway is about 25-30ft and it knocks the whole way up.


Went out for another ride together for around an hour; no noise, no problems. Had bikes parked on the street again for a few minutes while we moved the cars out the garage before putting them away. Jump on her bike, start it up and head for the garage...it's back knock, knock, knock.

I can't be sure where the noise is coming from exactly because it's not that loud and the bike has to be rolling (and hot) to get it to happen.

Anyone got any ideas what I have going on here?

JaY



"Veronica"
2002 VN750 Vulcan
Rebuilt Engine
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Pick-up Coils Gapped at .018"
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post #6 of 6 (permalink) Old 05-25-2011, 11:10 PM
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Next time the bike has the bumping feel to it, put it on the center stand and slowly spin the rear tire and check it for a lump in the sidewall or thread. Could be a belt in the tire separating and getting an air pocket as the rubber expands while hot. The squeaking your mrs. heard could have been air around her helmet and/or shield.
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