Rat-a-tat-tat!

davem222

davem222
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Hey guys,
So I just did a complete engine rebuild where I replaced a bunch of bearings, did Mike's 5th gear upgrade, etc and my bike has never run better....except for one thing. While riding, every 5-10 min, there'll be a loud RAT-A-TAT-TAT like a loose bolt clanging around inside the engine. There's no associated loss of performance, there's no stuttering in the throttle or rear wheel or anything like that. Has anyone had any similar experience? I'm really hoping someone will say something awesome like "It's no big deal, it's most likely..." but I don't want to get my hopes up.

Dave
 
I kinda figured, thanks Growl, lol, wouldn't want to kill myself on this damn thing :) I torqued the head when I put the engine back together but haven't really ridden the bike all that much since. I suppose I could retorque them just to be safe. Could it be the transmission slipping or anything? I mean, I wouldn't think so since there's no lapse in performance. I went out and checked the timing today just to be sure it wasn't detonation or anything and it seemed spot on.
 
So past combustion leaking past the head gasket (as Growl suggested) and possibly a loose header banging into the head (as TwoManyXs suggested), anyone have any thoughts on this? I don't think it's any of those things really. Could it be my drive chain maybe? I honestly don't think it's a loose bolt or anything in the case as I JUST rebuilt this thing.
 
Hey, Dave, a momentary drop in oil pressure or delivery could cause rattling. I had to drill/tap a fitting hole on the front of the right side cover to run a guage on my other XS. These bikes rely more on flow than pressure, so don't expect to see much over 12-15 psi. Just another thought...
 
Could it possibly be the drive chain?

....yeah, seriously look at this.

I bought a hardtailed XS650 from a dude a year or so ago. He sold it fairly cheap because of a similar noise.

He was convinced it was a cam chain noise....and the sky was falling.

.......I could see where the chain was whacking the rear fender so I snapped it up.
 
Phantom noises are disconcerting - the imagination can run wild. If you can hear it while you are running it may not be an engine noise at all (chain, etc). One noise I have at certain revs is a short series of repeated clunks resonating through the tank.

Can you identify exactly the area the noise is coming from.

Is it possible for you to video an example?

Anlaf
 
Good call guys, I inspected the drive chain near my fender on my hardtailed xs, sure bough there was wear at the spot near where the bottom half of the chain runs. Also the chain was far too loose (3/4" each way rather than total). I pulled the fender, cut it back and then tightened the chain last night. Im working all day but as soon as I get home Im going to take her for a test toast and see. With any luck that was the clanging noise. Fingers crossed. I'll keep you posted but thanks for all the help :)
 
I kept constantly adjusting mine to keep it from flopping into the fender. I finally gave in and bought a skate wheel chain tensioner. I went bolt on....took 20 minutes over a year ago and no chain adjustment since.
 
Seriously :) I have noticed that my chain is maybe a BIT more wobbly than I'd like, perhaps because the drive sprocket and wheel sprocket aren't 100% lined up properly. I'll have to figure out how exactly to line them up so that the chain runs perfectly :) But seriously thanks for all your help, especially 2Many, lol, I never would have gotten to that engine breakdown without you :)
 
Davem22, this thread has been useful to me - I was riding today when my intermittent clunking rattled through the petrol tank. I stopped and found gouges on the false oil can from the drive chain - that carried through the frame and resonated in the petrol tank. One drive chain adjuster mechanism on my Christmas list.

Mystery knocking solved.

Anlaf
 
I had the same chain slapping problem on a norton commando chop years ago. It would only do it at certain RPMs.
 
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