E: Engine Fitting a Norton Gearbox

Cyborg

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vibrac

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Dont forget that since the AMC box clutch actuator can rotate its no problem to make a second clutch cable exit further round the box I was shown it done using those low temp welding sticks that changed my mind about them
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Monkeypants

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Don`t Forget the power Output of a commando in relation with a Comet.In the Comet the gearbox has an easier life and the shafts and bearings are a minor Problem.Erik
This is true.
The 850 Commando is quite a bit harder on the gearbox than the 750 and a 750 pumps out roughly twice as much grunt as a standard Comet.
I would still be inclined to change out that layshaft bearing as it's cheap and easy to do whereas the lock up doesn't always go well!
It's the cage that lets go, don't know if it's due to power levels or just use over time.
The 850 tends to beat up on the bushings, one skimpy bushing in particular.
Probably no worries there with the Comet.

Glen
 
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Jez Nemeth

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Agree they're pretty good those sticks with care -moved the boss twice already with that method, then 1/4" BSF tap. One point, did find putting the boss too far over to the left when looking at the cover from side, position of the battery tray can interfere with the clutch cable alignment, and its easily done even with all the careful measuring -particularly when applying final tension to the gearbox adjustment for clutch and primary chain/belt. I originally had the boss placement right for chain, then made a belt drive system for the primary drive - they tension differently, about 1/2" difference on the adjustment arc. . .
 

Jez Nemeth

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Worth doing, Norton clutch came with the gearbox -bought a Commando belt clutch basket, front pulley, which was mated to part of the ESA sliding onto the crank spline, E10 belt, nut and split pin for safety... the final drive chain and sprocket set up aligns well, Commando 18T gearbox sprocket, 48T Vincent rear -only issue is the chain, a 530 needed for the front sprocket if using a Commando one, it gives some lateral movement on the narrower rear 48T Vincent sprocket, which I've assumed is for a 520, seems to work fine. Started with 108 links 18T/48T as per flash spec (Could possibly get a 19T front or even 20T?). Reduced chain length to 106 links to maintain nimble wheelbase.
 

davidd

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The stock Comet chain is 530 or 3/8" roller width, so the CS sprocket and the rear sprocket should match.

The Flashes and Lightnings used 520 or 1/4" rollers. The primary ratio of the Flash was 23 engine and 42 clutch, thus, 1.83. The racer has 36 engine and 68 for the Newby, which gives 1.89. The stock Comet is 23 engine 40 clutch, which is 1.74 primary ratio.

David
 

Robert Watson

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Or re ring the front sprocket to a 520. This is a Vincent 21T one but I have done them, AMC, Burman and others. I have rings in 18, 19, 21 and 22T in 520 and 530 widths. There maybe some still with a mate in the UK if you are interested.

The rings are SAE 8620 case hardened and we have several in service with 20K plus miles on them.


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Black Flash

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Hello Jaz,
Looking at your pictures in post #10, I think you could possibly use the reverse camplate. I am until now using a commando kickstart that has a bend in it to bring it further to the back. Now when kicking to the bottom, the kickstart is further to the front, hence hitting the reversed gear lever and engaging first gear. With the kickstart in your picture I believe you won't have this problem.
Also I admire your Vincent inspection cap on the norton outer cover, great job!
 

Chris Launders

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There is a massive range of sprockets available for the Norton box and several different internal ratio sets so you should be able to get exactly what you need easily enough, I agree with changing the layshaft bearing to a roller, I automatically do it, I'm not sure if you can get a reverse cam plate by just pushing the shaft out and pressing in from the other side or not.
If you are running a dry primary fit a pushrod seal, available from Norton stockists but I have made my own using another mainshaft nut with a 1/4" penny washer brazed on and a bit of 1/4" thick rubber cut to a disc that will fit inside the nut and a 1/4" hole punched in, fitted to the shaft end with a drop of loctite with the rubber squeezed just enough to cause a little drag on the pushrod.
 
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