Tappety Noise

Fastback-DE · Apr 30, 2026

Hi!

My 750 has developed a tappety noise after a run on the Autobahn - i wasn't going that fast, but maybe 90mph for 6 miles or so.
I've checked the valve clearance, and they were on slightly looser than when I set them last, and also adjusted the cam chain, which was a bit loose.

Where else should I be looking?

Cheers

Esben

Torontonian · Apr 30, 2026

Re-torque the head . The barrels too, start with that . Re-set valve clearances after , cold .
Re-tighten exhaust nuts , and any other things that would get looser .
Sure wish I was with you to run at that 90 Mph . You only have the 401 Hwy . here in Ontario . Risking suspension of licence etc. We are in KMS. Enjoy .

ashman · Apr 30, 2026

Fastback-DE said:
Hi!

My 750 has developed a tappety noise after a run on the Autobahn - i wasn't going that fast, but maybe 90mph for 6 miles or so.
I've checked the valve clearance, and they were on slightly looser than when I set them last, and also adjusted the cam chain, which was a bit loose.

Where else should I be looking?

Cheers

Esben

Not all old Nortons run quiet and at high speed best to have slightly lose tappets than tight, as cam chains with the stock adjuster they should be done every 10k miles as part of maintenance, at running higher speeds sounds do change and also oil plays a big part in what you run with, if the bike is running good then just enjoy the ride and do the maintenance when due.

velo54 · Apr 30, 2026

Check the primary chain tension. They rattle against the case if too loose. Graham

ashman · May 1, 2026

velo54 said:
Check the primary chain tension. They rattle against the case if too loose. Graham

Yeah the primary chain slap.

Fastback-DE · May 1, 2026

I'll check all of those, but i still think it's something at half engine speed. The noise is quite metallic sounding and fairly loud.
Is there anything else in the valve train that's known to be problematic?

Thanks!

Esben

kommando · May 1, 2026

The crank gear that drives the chain gear, if the keyway slot wears then the gear will slop back and forwards with the spring pressure from the valves moving the chain slack and then taut on the top run. I had this on a B40 and it sounded like a top end noise but the gear was loose on the crank and the keyway worn. New gear and key fixed the noise.

Fastback-DE · May 1, 2026

kommando said:
The crank gear that drives the chain gear, if the keyway slot wears then the gear will slop back and forwards with the spring pressure from the valves moving the chain slack and then taut on the top run. I had this on a B40 and it sounded like a top end noise but the gear was loose on the crank and the keyway worn. New gear and key fixed the noise.

I gave all the gears a good wiggle when I set the chain tension, albeit without removing the chain. Nothing seemed amiss, but I'll probably have to check again!

Lineslinger · May 1, 2026

Piston slap will make a racket you describe.

Torontonian · May 1, 2026

Lineslinger said:
Piston slap will make a racket you describe.

Yes , Pistons are finished . Budget for a teardown , build with new oversize pistons with matching rebore . Machinist stuff , credit card stuff . Hope I'm wrong . Enjoy .

ludwig · May 2, 2026

Dam

Fastback-DE said:
I gave all the gears a good wiggle when I set the chain tension, albeit without removing the chain. Nothing seemed amiss, but I'll probably have to check again!

Remove the plugs and turn the engine over slowly. A loose camshaft chain will cause a very audible click (camshaft jumps). No click: chain tension is ok.

ludwig · May 2, 2026

Fastback-DE said:
Is there anything else in the valve train that's known to be problematic?

Thanks!

Esben

The brased pads on the cam followers can come loose.
Did you notice a loss in power?

HRD · May 2, 2026

Fastback-DE said:
Hi!

My 750 has developed a tappety noise after a run on the Autobahn - i wasn't going that fast, but maybe 90mph for 6 miles or so.
I've checked the valve clearance, and they were on slightly looser than when I set them last, and also adjusted the cam chain, which was a bit loose.

Where else should I be looking?

Cheers

Esben

Have the cam followers been installed back to front and thus lack of lubrication to both cam and followers.

Fastback-DE · May 3, 2026

ludwig said:
The brased pads on the cam followers can come loose.
Did you notice a loss in power?

Maybe... I haven't dared giving it the beans....

Apparently, the engine had been rebuilt not that long ago by a specialist here in Germany, but I only havr a handwritten note to prove that. But it included Carillo rods, forged pistons etc.

Fastback-DE · May 3, 2026

If the pads on the followers have come off, wouldn't I have excessive valve clearance?
Or would the pad be loose, but roughly in the right place?

Cheers

Esben

hybridracer · May 3, 2026

Fastback-DE said:
Maybe... I haven't dared giving it the beans....

Apparently, the engine had been rebuilt not that long ago by a specialist here in Germany, but I only havr a handwritten note to prove that. But it included Carillo rods, forged pistons etc.

It is clearly non-standard so what else was changed and how many miles ago? A different camshaft would almost certainly need different tappet clearances to standard. I had a follower pad break across the middle. The cam pushed half of it into the bottom of the crankcase taking part of the follower tunnel with it. It sounded like a jackhammer going off. The fault was blatantly obvious when I checked the tappet clearances.

ludwig · May 3, 2026

Fastback-DE said:
If the pads on the followers have come off, wouldn't I have excessive valve clearance?

Yes you would.
I did not suggest this was your problem, but only answered your question about known weak points in the valve train.

franko · May 3, 2026

A rotor coming loose of its center can also give a similar sound. I've had a couple of them. First one took a long time to figure out. A mechanics stethoscope would help isolate where the noise is coming from. Me, I just use a piece of tubing.

ashman · May 3, 2026

A long handled screw driver work well on chasing noise screw driver on the engine and ear on the handle work great chasing noises.

Lineslinger · May 3, 2026

Mechanics stethoscope is a good idea. It will help give you a clue as to th location of your noise.

Tappety Noise

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