T140 Ringing Noise From Engine

[gumpt1oo]

My T140 has developed what can only be described as a ringing noise from the engine.
I runs fine, idles fine, but at exactly 4000rpm the ringing noise and vibration starts and at 4500rpm it stops. It does it the same in any gear. It does it at the same revs whilst accelerating or decelerating and it does it when stationary out of gear.
The only thing I can think of is the bores about ready for a re-bore, so could this be piston slap?
Or could it be cam bushes? When I rebuilt the bottom end 2 yrs ago I did not replace them as they were all ok.
I have checked everything else I can think of, tappets, re-torqued the head, primary chain tension and everything is fine, so I am a bit baffled!

 

[otherwise]

Quote,
"could this be piston slap?"

I suspect not. I've found piston slap on Brit classics to sound like a hollow or low pitch knock under load and a similar dull rattle when throttle shut.

This may sound a bit silly but Norton twins can make strange noised if the oil isn't getting away from the top end quickly enough. Check the oil system for normal return to tank if you can, I've never had an OIF bike, only tanks with good inspection option.

 

[gumpt1oo]

Well I am pleased to report that I have found the problem and it is nothing to do with the engine thankfully.
I was washing the bike down tonight and noticed that the lug on the front mudguard stay had broken off and the noise is the mudguard vibrating against the stay! I was convinced the noise was from the engine, time to get a hearing aid I think!

 

[devo]

Aha
Thats the kind of discovery that makes you feel good.

 

[otherwise]

A nice easy fix.

 

[CarlS]

An easy and cheap fix. Glad you found the problem.

 

[Rocky]

I'm glad it was only something simple.
I couldn't imagine a "ringing" noise from the engine.
Dull rumbling, knocking, slapping and thudding maybe, but I never heard of ringing.
My BSA 441 has chrome shrouds over the rear shock springs and at certain revs they "jingle"

 

[Village Idiot]

Oddly enough, I had that same thing happen to me on my '70, many years back. Had forgotten all about it. Glad it was an easy fix. Jim