Tappety Noise

DennisMo · May 4, 2026

I use a 4 foot length of cut garden hose as a stethoscope. One end at my ear, then probe around with other end until noise source is found!
Dennis

Lineslinger · May 4, 2026

I used to do that in the 60's. working on the family lawn mower, an MG 1100 and a 68 Fiat.
I have since broken down and bought a mechanics stethoscope at Harbor Freight for a whole $7.00

DennisMo · May 4, 2026

I had a Fiat 124 Sport Coupe. Beautiful and sweet motor. Except Rust........

Lineslinger · May 4, 2026

Methinks you missed the meaning of my observation

Fastback-DE · May 7, 2026

Hi again,

I'm not making much progress...
The primary chain was a bit loose, tightened that, and removed the locking tabs for the exhaust nuts, which were rattling.
I've tried to capture the noise on video, not sure if that helps...

Fastback-DE · May 7, 2026

franko said:
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.

Rotor as in the alternator?

Cheers

Esben

Fast Eddie · May 8, 2026

As has been suggested by many already, use a mechanics stethoscope to pinpoint the location of the noise. They are cheap and very effective.

Fastback-DE · May 8, 2026

Fast Eddie said:
As has been suggested by many already, use a mechanics stethoscope to pinpoint the location of the noise. They are cheap and very effective.

I've just ordered one!

Thanks for all the suggestions guys!

Esben

cliffa · May 8, 2026

Fastback-DE said:
Rotor as in the alternator?

Cheers

Esben

Have a look at this thread ( there are others too). But there were a bad batch of Lucas rotors, so definitely worth checking yours. The ones in question are stamped 54212006.

N

Post in thread 'Lucas Alternator rotors'

Jan 26, 2015

The old type (numbered .......2006) with pressed-in centre tends to explode due to the loosening centre. The later type (numbered …….2298) has a welded-in centre and will not explode. Check this out before you refit the existing Lucas rotor to prevent severe damage!

Fast Eddie · May 8, 2026

Fastback-DE said:
I've just ordered one!

Thanks for all the suggestions guys!

Esben

Excellent!

The sounds they pick up are amazing, you will be amazed how well you can pinpoint where noises are originating from.

You might also be a little alarmed at first, it can kinda sound like the internals are hell bent on destroying each other initially, but you’ll quickly learn to tell the difference between ‘normal’ and ‘abnormal’ horrid noises !!

cliffa · May 8, 2026

Fast Eddie said:
Excellent!

The sounds they pick up are amazing, you will be amazed how well you can pinpoint where noises are originating from.

You might also be a little alarmed at first, it can kinda sound like the internals are hell bent on destroying each other initially, but you’ll quickly learn to tell the difference between ‘normal’ and ‘abnormal’ horrid noises !!

Especially on a 961 !

Fast Eddie · May 8, 2026

cliffa said:
Especially on a 961 !

Don’t need no stink in’ stethoscope for them !!

TRWham · May 9, 2026

DennisMo said:
I had a Fiat 124 Sport Coupe. Beautiful and sweet motor. Except Rust........

Designed by Aurelio Lampredi

DennisMo · May 10, 2026

The Fiat 124 was a 5 speed double overhead cam which was quite something for its day. It had a timing belt, not chain, that needed changing. Two barrel Weber and cruise control consisting of a knob on the dashboard that was a throttle cable. One pulled it out and twisted the knob to lock it! I added an electronic ignition which was a new thing in that day.

Fastback-DE · May 11, 2026

cliffa said:
Have a look at this thread ( there are others too). But there were a bad batch of Lucas rotors, so definitely worth checking yours. The ones in question are stamped 54212006.

N

Post in thread 'Lucas Alternator rotors'

Jan 26, 2015

The old type (numbered .......2006) with pressed-in centre tends to explode due to the loosening centre. The later type (numbered …….2298) has a welded-in centre and will not explode. Check this out before you refit the existing Lucas rotor to prevent severe damage!

nortonspeed

I've got the one with 2 timing marks, but I'll have a closer look and listen on Wednesday.

Fastback-DE · May 15, 2026

Hi again,

The stethoscope says that it's the gearbox making the noise!
I haven't extracted it yet, but will do so shortly. If I don't find anything obviously wrong, I'll also pull the engine....

Cheers

Esben

kommando · May 15, 2026

The driveside layshaft is a known weak point, the copper/brass cage breaks and then the released balls can drop to one side and then escape. So even if you find its ok change it to the upgraded bearing which is either a roller or a ball bearing with a special plastic cage. Other weak point is the very small distance between the layshaft and mainshaft bearings which can crack and the bearings then wallow out the housing.

The classic symptom of the driveside layshaft bearing failure is the kickstart dropping on its own driven by layshaft being cocked to one side, the bearing balls fall out and then get stuck between the gears potentially causing a rear wheel lockup. You don't have any of that so it's probably ok but do the upgrade anyway.

Fast Eddie · May 15, 2026

Sometimes, with an engine noise, it’s ok to run it and keep and eye / ear on things until it either proves to be nothing or makes itself more identifiable.

Gearboxes are different. As kommando says, if anything causes your gearbox to lock up whilst riding you're in potentially big trouble as even pulling in the clutch won’t save you. The consequences of that whilst riding at speed on the autobahn don’t bear thinking about!

So it definitely needs looking at if you’re sure it’s the source of your noise.

ashman · May 15, 2026

The thing with Norton motors if they don't make some tappety noise that is the time to worry, I was lucky when my layshaft bearing blew with 12k miles on it, it blew when I put it in gear to leave home it just went bang and lost everything, when I opened the inner gear box case all the balls were laying at the bottom of the GB and the layshaft was just hanging there, that happens in the 70s.
My mates Norton his layshaft bearing blew we were 100 miles from home, but he was able to engaged 4th gear and rode the Commando all the way home in 4th, was hard work slipping the clutch at Nambour at a set of traffic lights and a big hill to climb from the lights when the main highway went through Nambour but he made it home and was back on the road a few days later.

Ashley

Torontonian · May 15, 2026

ashman said:
The thing with Norton motors if they don't make some tappety noise that is the time to worry, I was lucky when my layshaft bearing blew with 12k miles on it, it blew when I put it in gear to leave home it just went bang and lost everything, when I opened the inner gear box case all the balls were laying at the bottom of the GB and the layshaft was just hanging there, that happens in the 70s.
My mates Norton his layshaft bearing blew we were 100 miles from home, but he was able to engaged 4th gear and rode the Commando all the way home in 4th, was hard work slipping the clutch at Nambour at a set of traffic lights and a big hill to climb from the lights when the main highway went through Nambour but he made it home and was back on the road a few days later.

Ashley

Mine blew at 12000 kms . too . Limped home slipping the clutch in 2 nd . gear .
Always replace the bearing on the layshaft if it's an unknown history bike . Roller is my choice .

Tappety Noise

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