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Cam chain tensioner????

Big T

Big T

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I did a high RPM burst (past redline) chasing my buddy on his XN85 the other night and afterwards my bike was making a loud noise

It's a rotational noise that goes away after 2K rpm. Sometimes it's just a noise, sometimes it's really loud

It sounds like a rotary valve two stroke, nuts and bolts in a rotating coffee can

Listening around the motor, it's loudest on the left side, at the back

My 1st thought was the starter clutch, as I just replaced that 3 months ago. I pulled the stator cover and everything was tight

That leaves the starter motor and the cam chain tensioner. The starter motor shouldn't be the problem unless the starter clutch is bad

I just did a 110 miles run. Above 2K rpm, no noise. Below that, it may/may not start making the noise and the noise may come and go, or be really loud

So, process of elimination leads me to the cam chain tensioner. I rebuilt the motor about 15K ago and I occasionally take it past redline in 2nd or 3rd


Naturally, this happens 3 days before the rally
 
Mine does the same thing also...its quiet at start, and starts tapping after a few minutes of warmup. Between 2000 -2500 rpm its noisy then stops above that. The sound also varies in intensity....
 
Providing that you have a pressed together crankshaft. I have heard some possibly similar noises in that area after either the left hand of crankshaft has bent and also if the crank has twisted a little. Usually after shutting the motor down abruptly from high rpms. Like you explained. You also explain a rotational noise and if any of the above has happened it is possibly the main bearings that is causing the noise by the crank spinning out of true in them. Also if the crankshaft is bent at the left hand side where the charging rotor is it will cause the starter clutch drive gear to be off centered and also cause a rotational noise by loading and un loading it against the starter drive gears. Therefore that is your noise in the starter motor area. And also spinning out of true in the main bearing on that side can make a rattling or whizzing type noise at certain rpms. Hopefully neither has not happened and you find something else. Good luck :(
 
I don't think I spun the crank, it's welded

The bike runs great, pulled hard at all speeds with a passenger on board
 
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How about that clutch basket? Those springs on the backing plate can make a ruckus, especially if they're loose. How did you determine the starter clutch was tight?
I've personally seen threads from the bolts showing through the rotor with no heads or heads that snapped off and were rotating in there captured holes.

No performance deficiencies with noise?
 
The clutch was redone some time ago and there's no change in the sound when you pull the clutch lever

It's definitely on the starter side - I can't get the rotor off, may have loctited it on

The starter clutch pack wiggles, so I'm thinking that the 3 screws backed out
 
I have seen the bolts do as you say just back out a little and cause a rattling noise also. Also seen them sheared off. If they are not broken off most of the time you can just Loctite them and re torque them. You should closely inspect the bolts though if they are not broken for stretching, flat spots, etc.to stop any future grief from them loosening back up. When tightening or replacing the bolts take a center punch from the inside of the rotor and cinch the bolts by hitting them off centered a couple times to insure them against backing out again. If you need to replace the starter clutch in the future you can just take a small die grinder to the punched area of the bolts to get them back out. :cool:
 
All 3 bolts were loose and battered

Off to Ace Hardware, new bolts installed with plenty of Locktite

I'm thinking that the locktite didn't cure last time, as I was at my machinists shop and drove home 20 minutes after it was buttoned up
 
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