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Author Topic: Thumping noise  (Read 854 times)

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Offline taxiscooter

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Thumping noise
« on: December 02, 2008, 02:07:53 PM »
I have a 750k7 that makes a thumping noise. I noticed it at first when I made a rolling stop with the clutch in. I accelerated it back up to about 20mph and pulled the clutch back lever in and I could feel a thumping thru the foot pegs. Wasn't noticable accelerating or slowing down with the clutch engaged. Maybe the engine vibration was masking it.  It seems to cycle at an interval equal to one chain length or maybe one wheel revolution. The chain and both sprockets are well lubricated and the set have about 2000 miles on them.  Any ideas?   Thanks
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Offline shoemanII

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Re: Thumping noise
« Reply #1 on: December 02, 2008, 02:22:15 PM »
first thoughts are: out of balance wheel, balanced wheel that threw a wheel weight, "tight spot" in chain, loose rear sprocket bolts, tire damage (sidewall bulge, run over a curb lately?), busted spoke(s), out of true tire or rim.  i'd check all the free stuff first, then get both wheels spin balanced if you don't find anything.
bobp   
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Offline cafe750

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Re: Thumping noise
« Reply #2 on: December 02, 2008, 02:22:29 PM »
Is the chain properly adjusted?
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Offline taxiscooter

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Re: Thumping noise
« Reply #3 on: December 02, 2008, 03:26:23 PM »
At 2000 miles ago, had new ek o-ring chain, JT front and rear sprockets. Lubed chain every 200 miles. Also at that time new rear brakes, new tire and tube, and had the wheel trued and balanced.
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fuzzybutt

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Re: Thumping noise
« Reply #4 on: December 02, 2008, 03:35:27 PM »
loose motor mount bolt maybe?
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Offline Sam Green Racing

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Re: Thumping noise
« Reply #5 on: December 02, 2008, 03:48:13 PM »
Quote from: taxiscooter on December 02, 2008, 03:26:23 PM
At 2000 miles ago, had new ek o-ring chain, JT front and rear sprockets. Lubed chain every 200 miles. Also at that time new rear brakes, new tire and tube, and had the wheel trued and balanced.

That was 2,000 miles ago, check these things again.

Sam. ;)
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Offline jreich

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Re: Thumping noise
« Reply #6 on: December 02, 2008, 03:56:12 PM »
I'm sure this is entirely too simplistic...but I try to make that my usual starting point; how is your oil level? When did you change it out last?
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Offline Thunder

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Re: Thumping noise
« Reply #7 on: December 03, 2008, 08:19:46 AM »
I had/have exactly the problem you are describing. My bike tho, HAD, been sitting for 2 years.
It seems to be the chain, but doing my rebuild slowly(insert cheapskate ;)), i decided not to spring for a chain just yet. ??

Took alot of the advice offered here when i queried the same thing.
http://forums.sohc4.net/index.php?topic=42920.0

put the bike on centre stand (i took off the engine cover hiding the front sprocket and replaced the main cover) then start the bike and watch the chain. Probably a tightspot.

i took the bike for a spin (warming the chain up) then put it back on the stand and sprayed it liberally with penetrating oil (just to loosen the links).

it's not right yet but its definetly getting better...

Good luck
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