Norton Box Layshaft Gear

brian gains

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Reading the thread in the technical section with regard replacing the Comet Burman box with Norton box. I have one question which I didn't want to hi jack the thread with.
There are numerous mentions of the Norton layshaft gear roller bearing self destructing and therefore prudent to replace with a bush. Is this a well known/standard mod'when fitting to a big twin. I like to think my chopped motor hasn't got this far without the mod being carried out but am slightly twitched none the less.
 

erik

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I ride my commando since 34 years and my experience is that the original gearbox case is weak where the two bearings of main- and layshaft come close together. i replaced the case by a quaife case which is much stronger in this area.Any movement of the bearing in the case will destroy it sooner or later.Regards Erik
 

brian gains

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so it is a well known weakness and it would be reasonable to expect this to be addressed by knowledgeable Vincenteers when adapting the box to a big twin.
 

davidd

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I think it is a problem that is well-known in Norton circles, but not in Vincent circles. I certainly would use high-quality bearings. It was the brass cage that seemed to break in the originals.

I have only used the Commando box on a racer and then for only a few races as it is illegal. Having installed the TTI box, which is far superior and legal, I never looked back. The original Commando box in the racer was built by John Renwick, whom I would believe, knew how to properly build the box. He is the only person I know that has run a Commando box on a twin. That bike won at least two national championships.

MickyCarter Buller Renwick01.jpg


Chris uses the roller and others, like Mick Hemmings, are partial to the steel and phenolic caged special ball bearing. Both seem to produce good results.

David
 

Chris Launders

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I've had a Norton box/Commando clutch in the Norvin for 20 years, no problems, that's a twin running 34mm Mikuni's and MK2 cams.
 

Monkeypants

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so it is a well known weakness and it would be reasonable to expect this to be addressed by knowledgeable Vincenteers when adapting the box to a big twin.

I wouldn't count on Vincenteers or Nortoneers knowing about this problem.
Every now and then, on the Norton forum, an owner will post up about a lockup or ask why the kickstart is banging into their leg.
Some have been riding for years but aren't aware of the issue.


Glen
 

brian gains

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David: if John Renwick puts them together that way i'm in the clear, or at the very least have a high degree of confidence.
ps that machine looks the dogs wots nots, any more photos, spec', utube clips available on line?
 
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davidd

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575 MPH has a photo of the twin and the single when Vic Buller owned it. I think the photo above is when Mickey Carter had it.

Unfortunately, Vic discovered a crack in the twin case that started at the oil filter, traveled by the main bearing and continued toward the clutch. I hope the bikes are still around as they are are the real deal.

Graham Buller on the single:

Graham Buller Mallory 1993.jpg


David
 

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