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Mk ll intermediate gear #785034 09/22/19 2:38 am
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Samsmc1 Offline OP
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Can anyone tell me why Norton changed the cam drive intermediate gear for the Commando Mk lll? I'm building an engine from pieces mostly Mk lll, but with some other bits thrown in the pile I started with.
The cam sprocket is the same, therefore there shouldn't be an alignment problem for the chain.
Is there any reason I can't use the older intermediate gear assy?
Thanks
Sam

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Re: Mk ll intermediate gear [Re: Samsmc1] #785128 09/22/19 11:15 pm
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Dave Comeau Offline
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The MKIII is a very significantly different engine from all the previous versions. The crank is longer and the cases are wider. The timing chest had to be altered to keep the cam and oil pump in a similar position. A high skill or experience level is required to navigate all the variations of the norton heavy twins evolution. 1949-1975. I've worked on them all...


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
Re: Mk ll intermediate gear [Re: Dave Comeau] #785139 09/23/19 12:35 am
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Rohan Online Content
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Much chest thumping - but is there an actual answer there anywhere !?

Cheers !

Re: Mk ll intermediate gear [Re: Dave Comeau] #785180 09/23/19 11:27 am
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Dave Comeau Offline
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Originally Posted by Samsmc1
Can anyone tell me why Norton changed the cam drive intermediate gear for the Commando Mk lll?



Originally Posted by Dave Comeau

1.The MKIII is a very significantly different engine from all the previous versions.
2.The crank is longer and the cases are wider.
3.The timing chest had to be altered to keep the cam and oil pump in a similar position.

4. A high skill or experience level is required to navigate all the variations of the norton heavy twins evolution. 1949-1975. I've worked on them all...


This experience with enough research will show that
A. 21 years the NHT had a twin chain engine.
B. 4 years the NHT had a single chain engine.
C. The last year only of NHT (MKIII) had a different wider engine... see above.

Pretty clear to the most casual observer...


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
Re: Mk ll intermediate gear [Re: Samsmc1] #785195 09/23/19 2:01 pm
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Originally Posted by Samsmc1
Can anyone tell me why Norton changed the cam drive intermediate gear for the Commando Mk lll?


As explained by DD.


Originally Posted by Samsmc1
I'm building an engine from pieces mostly Mk lll, but with some other bits thrown in the pile I started with.
The cam sprocket is the same, therefore there shouldn't be an alignment problem for the chain.
Is there any reason I can't use the older intermediate gear assy?


The 850 Mk3 intermediate gear is thinner so there would be an alignment problem with the wider pre-Mk3 gear (and the timing cover wouldn't fit).

The Mk3 crankshaft pinion 06-5670 is also thinner.

https://andover-norton.co.uk/en/shop-details/16604/crankshaft-pinion



Last edited by L.A.B.; 09/23/19 2:01 pm.
Re: Mk ll intermediate gear [Re: Samsmc1] #785204 09/23/19 3:27 pm
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Samsmc1 Offline OP
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OK - I understand what's going on now.
i had a reply in a previous post from Gregg stating that the covers were interchangeable but I didn't pay close attention to exactly what he said .

The MKIII covers are interchangeable with the older covers with a few mods (like the flat pump seal to allow the plunger to seat). I even updated a very early 20M3 Commando engine with a MKIII cover years back, though on that one I had to machine back the boss in the timing cover that supports the idler gear shaft.
.. Gregg *************************************************************************************************

Thanks
Sam

Re: Mk ll intermediate gear [Re: Samsmc1] #785261 09/24/19 12:30 am
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Rohan Online Content
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Golly gosh we got there.
Extracting Norton info is sometimes a bit like like being a dentist ??

Re: Mk ll intermediate gear [Re: Samsmc1] #785330 09/24/19 4:38 pm
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Samsmc1 Offline OP
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Rohan
I'm not sure that I agree completely with you analogy
Many times, we don't ask the proper question or read what was actually said like in my case with Gregg's reply.
thanks
Sam

Re: Mk ll intermediate gear [Re: Samsmc1] #785351 09/24/19 9:54 pm
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Rohan Online Content
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I've used that analogy before, but I'd agree that there are lots of different scenarios and minor technicalities.
I've commented before though that Norton info (sometimes) seems much tougher to nail down.
But they were not a big volume producer, so maybe thats to be expected.
These forums sure fill a big need, so we do pretty good, mostly.

Re: Mk ll intermediate gear [Re: Samsmc1] #785353 09/24/19 10:33 pm
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Samsmc1 Offline OP
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10-4 on filling a big need .


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