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New cam chains and tensioners didn't fix my rattle


Matty

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77000km on the bike. Rattle has gotten worse over the last 3000km while I waited for cam chains to arrive. While free revving, it is present between 3-4000rpm. On the road it is present from 3000rpm through the rev range with steady throttle and when backing off and cruising. I don't notice it when on WOT. The sound is more present from the rear barrel up with a stethoscope. No noise at idle.

 

New cam chains and tensioners made no difference. I have also tried manual tensioners with no change. Guides look ok with very little wear.

Any suggestions before I have another look for a possible crack in a guide I missed before or a sticking bucket?

 

 
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More troubleshoot is in order before you buy any more parts...

the noise in time with the crankshaft...  possible source of crankshaft

speed noises are a scuffed piston and stuck piston ring... damaged rod bearings...

 

To help pin point the exact location of the noise hold a long tip screw driver or a
length of garden hose up to your ear and probe the suspected area...

 

A skuffed piston will bind the ring from expanding in the bore resulting in

low compression and a rattle noise...  To pin point which cylinder might

have a skuffed piston take a compression test... focus on the weak one...

 

To check for a bad rod bearing set the engine at high idle and remove
one spark plug wire at a time... if the noise stops then that's the
cylinder with the bad rod... if noise continues after both spark plug
wires were removed then the noise is something other than a rod knock
because a rod will not produce a knock by just turning over the
piston... it takes the spark of combustion to produce a sharp metallic
sound...

 

 

SkuffedPiston1.JPG

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No change in noise with coil sticks unplugged one at a time.

With a stethoscope, I can hear the noise more from the rear cylinders but I could not notice a difference between the left and right.

A compression test delivered 95-97psi across the board, which is not within spec but a close range. It might be worth taking some more parts off to have a better look. I think you might be on the right page BusyLittleShop, I might be hearing some piston slap.

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1 hour ago, Matty said:

No change in noise with coil sticks unplugged one at a time.

With a stethoscope, I can hear the noise more from the rear cylinders but I could not notice a difference between the left and right.

A compression test delivered 95-97psi across the board, which is not within spec but a close range. It might be worth taking some more parts off to have a better look. I think you might be on the right page BusyLittleShop, I might be hearing some piston slap.

I read recently that compression readings will be low if the adaptor doesn't fit fully into the spark plug hole; the extra air volume reduces the compression ration. Just a thought. 

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Plus you need throttle wide open when doing compression test ! 
 

Sounds like cam chain or tappet noise to me, but if you replaced the chains & tensioners not likely to be that. Have you checked the Vtec valve clearance ? 

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