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Making one good Commando out of two donors.

Classic Norton Commando Motorcycles.

Making one good Commando out of two donors.

Postby Teabandit » Wed Sep 13, 2017 8:00 pm

Hi folks, I have a bit of a bitsa Norton Commando on my hands, I'll give you all the story/details and if you wouldn't mind just give me an idea of any issues I might run in to and anything to look out for while I give it a bit of a resto-mod.

Initially I bought (what I thought was) a 1973 850 Hi Rider turned Roadster, previous owner(s) had done away with the daft ape hangers, silly seat and slid it down the road a time or two by the way it looked. It now had US bars, Corbin seat and big old weld round the timing side of the crankcase. The thing kicked over and had decent compression but upon further examination when I took the engine apart for a refresh it was a real throw together, 850 bottom end bit of side play in the crank, a chewed up cam, worst I've seen and 750 Atlas barrels and head needless to say that the engine and frame numbers didn't match up. A previous owner had been in some form of accident and thrown the bike back together with presumably whatever he could get his hands on.

The fella I bought it off felt awful and had an unmolested 74' 850 Roadster as well with no gearbox which he sold to me for a real bargain for feeling like he'd screwed me over, he had no idea the bike was such a bodge job. Fast forward to today, I've done a top end refresh on the 74' 850 engine which seems all in good order and back together, I'm going to use it in my 73' frame/roller which was in better condition all round compared, bar the frankenstein of an engine.

As it stands I just want to get the bike running reliably and work on full restoration stuff as and when I can afford it. I'm taking the two Amals from the 74' bike as the 73' had a 30mm Mikuni which is the wrong size anyway for an 850. Using MkIII adjustable isolastics on the rebuild, from what I've gathered I need to take a bit off the front engine mount for it to fit right, that I know. New sealed wheel bearings, read mixed things about these as far as having to mill out the hubs or whether they fit right in? New fork seals and dust covers as well as rear shocks. Basically replacing and upgrading what I can of all the perishable rubber parts. The 73' bike also had a Pazon Ignition system which I intend to use, so maybe that means upgrading my coils as well, I hear they are rather thirsty.

Anything that you guys would advise and recommend? Hopefully that essay makes sense of my odd Norton situation. I already don't intend to sell the bike pretty much ever so the numbers thing doesn't bother me but I just want it running right, it's going to be my daily, eventually.

Many thanks from a 24 year old Brit, just moved to US a year ago, got more project than I bargained for! :shock:

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Re: Making one good Commando out of two donors.

Postby gortnipper » Wed Sep 13, 2017 8:58 pm

If you fit 4203 2RS and 6203 2RS bearings they will drop right in and you dont need to mill or use the felt seals/retainers.
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Re: Making one good Commando out of two donors.

Postby L.A.B. » Thu Sep 14, 2017 12:44 am

Teabandit wrote:Using MkIII adjustable isolastics on the rebuild, from what I've gathered I need to take a bit off the front engine mount for it to fit right, that I know.


Only if you fit actual Mk3 Isolastic parts. Not if you fit the pre-Mk3 vernier Isolastic conversion kit.
https://andover-norton.co.uk/en/shop-details/17047

Or, the Mick Hemmings conversion kit:
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Re: Making one good Commando out of two donors.

Postby grandpaul » Thu Sep 14, 2017 6:35 am

Since you are already doing some serious work to replace the isolastics, I would carefully examine all the components on both bikes, then select the best of everything to install onto the best/straightest frame.

Virtually EVERYTHING on those 2 bikes should work just fine in any combination you end up with.

LAB has already made the point that there are drop-in iso kits that don't require machining the front iso tube.

ALWAYS nice to have a spare bike, you definitely won't come up short on fastener hardware!
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Re: Making one good Commando out of two donors.

Postby eskasteve » Thu Sep 14, 2017 7:43 am

Good luck on your bike. You do know that once the first bike is done that you will be looking at the donor and thinking, "Hmmm, what if I were to just..." and off you go onto another project. Most of all have fun! What area of the US did you move to?

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Re: Making one good Commando out of two donors.

Postby rvich » Thu Sep 14, 2017 10:17 am

Is the 850 head an RH10? Might want to read up on Jim Comstock's porting and valve jobs. While you are at it put his breather on the back of the case. Investigate Kegler Clamps. Start thinking about a head steady. This is a short list to get started...but don't forget reading about brake upgrades, whether to use standard rims or to go wider, and don't forget to clean the kill switch and the ignition switch!

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Re: Making one good Commando out of two donors.

Postby Teabandit » Thu Sep 14, 2017 8:48 pm

rvich wrote:Is the 850 head an RH10?


I don't know, I'll have to find out, there is a chance it could be with it being 74'? Sorted a head steady and would like to do some engine mods at some point when finances allow it, as well as brake upgrades.

eskasteve wrote:Good luck on your bike. You do know that once the first bike is done that you will be looking at the donor and thinking, "Hmmm, what if I were to just..." and off you go onto another project. Most of all have fun! What area of the US did you move to?


I can imagine that's how it goes! I grew up and lived in Lincolnshire, UK for 22 years, moved to far west Texas last year, where I found the Nortons, the other half bike is actually still there, I need to pick it up. Now I live in Chattanooga, TN.

Thank you for all the pointers chaps, I did buy the Pre Mk III Vernier Isos so I should have no problems then? One more thing I've noticed is that the 73' bike forks/front wheel have the disc brake mounted on the other side, did Norton just run this for one year? I've not seen another one with it on the 'wrong' side?

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Re: Making one good Commando out of two donors.

Postby Mr. Rick » Thu Sep 14, 2017 10:50 pm

Up through the 74 models, the disc was on the right side. For the revised electric start Mark 3 of 1975, the disc was moved to the left side, using different shock sliders.
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Re: Making one good Commando out of two donors.

Postby Teabandit » Fri Sep 15, 2017 3:57 pm

Mr. Rick wrote:Up through the 74 models, the disc was on the right side. For the revised electric start Mark 3 of 1975, the disc was moved to the left side, using different shock sliders.


Cheers Rick, wonder if previous owner took a later front end post accident.

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Re: Making one good Commando out of two donors.

Postby L.A.B. » Fri Sep 15, 2017 4:08 pm

Mr. Rick wrote:Up through the 74 models, the disc was on the right side. For the revised electric start Mark 3 of 1975, the disc was moved to the left side, using different shock sliders.


The Mk3 'shock' (fork) sliders were, in fact, exactly the same parts as the pre-Mk3 fork sliders, just swapped over from one side to the other which then placed the caliper ahead of the slider on the LH side.
The Mk3 wheel/hub assembly is different.
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Re: Making one good Commando out of two donors.

Postby Mr. Rick » Fri Sep 15, 2017 4:33 pm

Once again I am gently corrected by someone who actually knows what's going on.
Thanks, L.A.B., and I'll be more careful in the future.
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Re: Making one good Commando out of two donors.

Postby grandpaul » Fri Sep 15, 2017 8:30 pm

Yep, MkIII hub bearing retainer has opposite threads to cope with opposite rotation.
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Re: Making one good Commando out of two donors.

Postby L.A.B. » Sat Sep 16, 2017 1:17 am

grandpaul wrote:Yep, MkIII hub bearing retainer has opposite threads to cope with opposite rotation.


The Mk3 front hub has a circlip bearing retainer [13]. :roll:
https://andover-norton.co.uk/en/shop-dr ... and-brake#
https://andover-norton.co.uk/en/shop-de ... 63/circlip


Teabandit wrote:wonder if previous owner took a later front end post accident.


Could be, but pre-Mk3 owners have been known to swap the assembly around (so placing the brake on the left side) as that is supposed to cure a tendency for the bike to want to pull to the left. If you find your hub has a threaded lockring and not a circlip then it's a reversed pre-Mk3 hub/wheel.


https://andover-norton.co.uk/en/shop-de ... -lock-ring
disc-brake-from-left-right-side-t5611.html
pull-the-left-cured-t1907.html
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Re: Making one good Commando out of two donors.

Postby grandpaul » Sat Sep 16, 2017 7:00 am

L.A.B. wrote:If you find your hub has a threaded lockring and not a circlip then it's a reversed pre-Mk3 hub/wheel.

I found one like that. I thought it was original...
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