67 N15CS Build

[acotrel]

The way the swing arm pivot is mounted is unusual. I like to have full circle rear engine plates with ends of the pivot spindle secured. With a dirt bike, it might not matter so much if you do not know where your rear tyre contact patch is, but the forces involved are still large.

 

[acotrel]

I have it boxed up and on a shelf. You might consider turning on the direct message function, so I could discuss details with you.

For the peanut gallery: I talked Chris out of buying the NEB clutch I have. It is a slightly difficult install in a P11 primary without trial and error modification. I would imagine it could be a similar PITA on a N15. The AMC clutch these old bikes came with is a bolt-on simple fit.

I use an early AMC clutch behind my 850 motor. I did not believe it would withstand clutch starts in road races - it is another thing which I under-estimated about Nortons. It copped 6000 RPM on a start line, and did not give up.

 

[Schwany]

I use an early AMC clutch behind my 850 motor. I did not believe it would withstand clutch starts in road races - it is another thing which I under-estimated about Nortons. It copped 6000 RPM on a start line, and did not give up.

My old AMC clutch was slipping on acceleration when I decided to replace it. I almost put it back in because I bought a new set of plates for it, but went with a diaphragm spring dry belt clutch, which for me is a better clutch with a lighter pull at the lever, and a lot less messy. It can take all the acceleration my engine can make and hold. I don't do 6000 RPM starts from a stop though. The exhaust note at 6000 RPM would draw a lot of unwanted attention on the street. Plus I don't like doing wheelies from a stop. Doing that makes me feel out of control and I wasn't born with the show off gene.

 

[Chris Johnson]

Thankfully, Schwany talked me out of buying his clutch. My goal is for reduced weight/stress where I can get it. I’m geared so low at 18/60 that I don’t think I’d miss the flywheel effect so much. It’s all moot, standard parts are in the mail to make my stock clutch right.

On a completely unrelated note - why doesn’t it seem like anyone is using triumph valve cotters in place of the Norton parts? They measure up the same and I can buy 3-4 triumph pieces for each Norton item. Alternately kibblewhite makes a tidy kit of HT cotters for a good price. What am I missing here?

Chris

 

[Schwany]

Thankfully, Schwany talked me out of buying his clutch. My goal is for reduced weight/stress where I can get it. I’m geared so low at 18/60 that I don’t think I’d miss the flywheel effect so much. It’s all moot, standard parts are in the mail to make my stock clutch right.

On a completely unrelated note - why doesn’t it seem like anyone is using triumph valve cotters in place of the Norton parts? They measure up the same and I can buy 3-4 triumph pieces for each Norton item. Alternately kibblewhite makes a tidy kit of HT cotters for a good price. What am I missing here?

Chris

I am not knowing, but I'll blab out something somebody that knows can disagree with and you'll get the right answer.

Best guess is Norton parts are over priced, or the Triumph collets don't actually work in Norton valve spring retainers.

 

[mdt-son]

Thankfully, Schwany talked me out of buying his clutch. My goal is for reduced weight/stress where I can get it. I’m geared so low at 18/60 that I don’t think I’d miss the flywheel effect so much. It’s all moot, standard parts are in the mail to make my stock clutch right.

The NEB clutch has shortcomings. A sprocket made of 7000 series dural will wear fairly quickly. NEB should have made a bolted steel sprocket for the clutch hub. I believe the fitting problems Schwany experienced can be solved.
With a steel sprocket, the GPV clutch would be an attractive option. An inventive person may be able to alter the clutch hub?

AMC's clutch design has much going for it. Unfortunately, the clutch is prone to oil contamination because of its open design. When subjected to the torque of a Norton engine, owners will often experience clutch slippage. This was noted even during testing of new bikes.
Cleansing of friction plates helps - for a while. Fitting an external shielding of a thin-walled alloy sleeve would probably help a lot.

Another possibility is adaption of a Triumph T140 clutch w/7 plate conversion paired with a Commando engine sprocket, running a triplex or duplex chain.

- Knut

 

[Chris Johnson]

Knut, I have a GPV on the bench that I bought used on the hopes the splined hub would work, but apparently the speedway bikes use bigger jackshafts.

I’d also prefer a steel bolted up sprocket as I see some companies offering as a repair service. But just spitballing dimensions based on Schwany’s experience, the chainwheel ends up about 3/16” inboard when the clutch hub is positioned correctly, and there’s not enough thickness to the clutch drum to step it, bolt up a sprocket and correct the chain alignment.

Alternately, the clutch hub needs a 3/16” snout added on the backside and the splines shifted to match (basically what Schwany ended up with to make his work). More work than I’m interested in doing.

Chris

 

[mdt-son]

Knut, I have a GPV on the bench that I bought used on the hopes the splined hub would work, but apparently the speedway bikes use bigger jackshafts.

Chris,

NEB Engineering provides a splined hub for the AMC / Norton mainshaft which fits Elite and GPV clutches.

- Knut

 

[Chris Johnson]

Chris,

NEB Engineering provides a splined hub for the AMC / Norton mainshaft which fits Elite and GPV clutches.

- Knut

Yea I’ve seen it. From what I can tell you get the same relationship from the hub to sprocket and the same alignment problem.

Oh yea… and the pressure plate isn’t adjustable for the pushrod.

Chris

 

[Chris Johnson]

I figured out the valve collet thing - Norton valves are 9/32” in diameter at the collet, the others are 17/64”.

Chris

 

[Schwany]

The NEB clutch has shortcomings. A sprocket made of 7000 series dural will wear fairly quickly. NEB should have made a bolted steel sprocket for the clutch hub. I believe the fitting problems Schwany experienced can be solved.
With a steel sprocket, the GPV clutch would be an attractive option. An inventive person may be able to alter the clutch hub?

View attachment 123103


AMC's clutch design has much going for it. Unfortunately, the clutch is prone to oil contamination because of its open design. When subjected to the torque of a Norton engine, owners will often experience clutch slippage. This was noted even during testing of new bikes.
Cleansing of friction plates helps - for a while. Fitting an external shielding of a thin-walled alloy sleeve would probably help a lot.

Another possibility is adaption of a Triumph T140 clutch w/7 plate conversion paired with a Commando engine sprocket, running a triplex or duplex chain.

- Knut

Give all your fixes for installing a NEB clutch in a P11 a try, and get back to me. lol

I did make it fit with a Commando mainshaft and put a few miles on it. Never did get perfect chain alignment, but fairly close. The Commando mainshaft wasn't that happy inside the P11 gearbox and shifting was problematic. I put the original mainshaft back in the gearbox so I could use the AMC clutch. Bought new plates for the AMC clutch, but was by then very tired of dealing with the oily mess and went to a RGM belt clutch. There are many issues that made it a poor choice for a P11 primary. I seriously doubt NEB ever installed the clutch in a P11.