My Model 50 screams at me...

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There's something weird going on with my Model 50. Sometimes a loud screaming sound appears. Bit like a slipping pulley belt, but not as high pitched. More like a rusty lorry brake or a really noise rim brake on an old bicycle.

It first appeared when I closed the throttle during a ride in town, but stopped as soon as the bike idled. It did that a couple of times, but then disappeared. Only to come back suddenly on AND off the throttle and even during idle. I stopped the engine, started it again and it was still there. Repeated this and the sound was gone. It came back once or twice ff the throttle before I got home.

I discovered that the magneto bearing was extremely loose, as the insulator washer seemed to have had it. After replacing with a thicker paper, I really had to drive the outer bearing race home. Job done.

Yesterday, I was out on the bike and it behaved perfectly. But today, I started it and the dreaded screaming began. No clutch, just direct after kicking it. It's really loud, even louder than the exhaust. A blip of the throttle and it was gone again. I pulled in the clutch, put it in first and all was still fine. Letting the clutch grip and pulling away, and there it was again, screaming at me. I released the clutch, but the screaming continued.

Engine off, kickstarted it and all was well again. Blipped the throttle and it began screaming once more. To be honest, I felt like joining in at this point. I pushed the bike in the shed and walked away for a bit. Later, I checked the magdyno and the bearing and insulator are fine. What else could make this screaming sound? It does sound like something is spinning/freewheeling/slipping with a really loud resonance.

On the primary side, all is well. Engine sprocket secure, chain as it should. The clutch doesn't seem to have any effect and works as it should, as does the gearbox.

This one has me stumped to be honest. Any suggestions?
I know it's really hard to describe a sound, but with the explanation above, I do hope you can get some sort of an idea.

Cheers,

Tim

Not just a Norton

I once bought a B40 with the same symptoms. It turned out the gearbox had no oil in it whatsoever.

Is some part of the clutch…

Is some part of the clutch touching the primary cover, inside or out? And is the felt seal retainer in the inner primary behind the clutch damaged? That wouldn't be easy to see.

If you've got a "short"…

If you've got a "short" generator the plain bearing will scream sometimes if it's running a bit dry (I've had this happen on my ES2!).
John

Hi Tim These bikes must…

Hi Tim These bikes must have some sort of telepathy thing going on, took my 1959 model 50 for a short ride today and it screamed at me in a similar manner as yours! After it had cooled of went out to start investigating and it was making the noise even as I tried to kick it over. Think it is coming from the clutch area. Will have a more in-depth look tomorrow.

Sounds like a bearing has…

Sounds like a bearing has seized to me and it's either spinning in its housing or the shaft is spinning inside the inner race. Use the old fashioned trick of putting a stick of wood or a long screwdriver against your ear and the other end against the engine and gearbox in various places until you can hear where it's coming from.

Lots of possibilities

Thanks all, that are a lot of possibilities!

The gearbox is well-filled with oil and I had the magdyno apart just weeks ago (in a bid to cure the sound), when I greased and oiled the bearings. The sound did disappear after that, but is back in all its glory now. The clutch works as it should without slipping and the primary cover isn't showing any rubbing marks. A felt seal (and its retainer) are on the list to be added, so they're now not there.

I'll put everything back together again and will bring a long screwdriver with me on a test ride. If the sound appears again, I'll have a good listen. But it's on and off, not constantly, so this could be tricky.

Any findings on your side Richard?

Hi Tim i took the primary…

Hi Tim
i took the primary outer cover off and then started the bike. It was making the screaming noise all the time, even when I kicked it over before it started.

I have been running the bike with no oil in the primary as I haven't got it oil tight yet ( I have only done about 4 miles on it this season so far so not to concerned about running dry.

I sprayed some oil around the clutch area and tried to get some behind the clutch basket in case it was the seal at in the inner cover.

When I restarted the bike after a few minutes of spraying the oil the screaming had gone! Not sure why it was making the noise and no doubt it will return when I have an audience!

Update

It's annoying when a problem disappears without actually exposing itself, isn't it?

I started the bike up tonight, to try and localise the sound as per Bob's suggestion and maybe try to record it.

NOTHING!

All I did was put the magneto sprocket back on, so I can't have solved anything.

If old Nortons have a sense of humour, mine must think he's Bennie Hill...

I'll start it the next couple of days. Maybe take it up and down the road and hope the sound returns.

For now, only two words can sum it up: 'barking' and 'mad'.

Let's see if the sound reappears first on mine or Richard's. And who can identify it first. In that regard, I could be 0-1 behind...

Stripped the primary side…

Stripped the primary side down today. Both inner and outer covers. When I removed the clutch hub the felt cover for the main shaft was lose just as David C had suggested. It was spinning around with the main shaft but not all the time. That is probably why the screeching noise is intermittent. Hopefully, when I sort it out that will cure it. We will see.

Could it be...

... the dynamo fibre clutch slipping?

That sounds absolutely…

That sounds absolutely plausible and would definitely be in line with the sound that I'm hearing. Especially as it appears or disappears with going on or off the throttle. I'll have a look this weekend.

If I remember correctly, the one on it is quite battered.

Could it really be that simple? I won't have my hopes up just yet, but am keeping fingers firmly crossed.

If...

... you just pop the dynamo off that would eliminate the fibre clutch.

@Richard I really hope for…

@Richard
I really hope for you it's indeed the felt cover! I don't have one, so my search continues. Though I have my hopes up regarding the magdyno fibre gear spring.

@Ian
I'll replace the spring/clutch anyway, as the one that's on definitely had been battered. It's quite (inconsistently) dented and bended. A new one is just under 4 euros. I'll give an update after Saturday.

A short update: I found a…

A short update: I found a new clutchspringwasher, but haven't replaced it yet. I'd like for the sound to appear one more time, so I can trace it better with the long screwdriver I keep driving around with now. Problem is, that the Norton now behaves perfectly...

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