What To Build

Norcoastal said:

I’m staying MK1. Nothing after ‘73 if I can help it.

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There are a lot of MK 3 items that are worth adding it seems. Youll find thread after thread about converting to MK3 this or that. T
MK3 vernier isolastic switchover is a favourite.
I started a thread listing the differences between a MK3 and Mk2 or MK2a, both of which have improvements over earlier bikes.
I've found a number of small MK3 improvements since and haven't added them to the thread, but this gets most of it.


https://www.accessnorton.com/NortonCommando/mk3-changes-from-74-models.18871/

Some of the MK3 stuff is worth doing, some probably isnt.
For example, the swing arm and rear wheel have multiple improvements over earlier bikes, but might be too much effort.
On the other hand, you could use that whole back end and end up with a stronger swing arm, sealed pivot bushings, proper cush drive and cottered swing arm pivot. The cottered swing arm is a solution to an earlier swing arm pivot issue that results in poor handling. The stiffer swing arm is also a handling fix. I guess the sealed bushings are also related to handling as worn out swing arm bushings are a handling negative.
You would also have a rear disc brake, maybe not important, but it is a nice brake.
Some have just adapted the MK3 swing arm to an earlier bike, but stayed with a drum brake.

Glen

If you stay with 73/74, MkI, MkII across the board, you'll be fine and have a decent build in the end.

MichaelB said:

If you stay with 73/74, MkI, MkII across the board, you'll be fine and have a decent build in the end.

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That’s actually my plan.

thanks

Of course you can build one of these!



Just in case you haven't discovered it yet, there is a shop in Colorado that does some custom stuff. https://coloradonortonworks.com/

Just be warned, the gallery is kind of addictive! So is the parts department. Hand your wallet to your spouse before entering.

Here's another one that will inspire: https://nycnorton.com/

FYI, those beautiful cylinder heads and cases you see at CNW and NYC, have probably been Vapor Blasted/ or Honed as some say.

Norcoastal said:

That’s actually my plan.

thanks

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You'll likely end up with a couple of MK3 items almost by default.
The MK3 vernier type isos are a no brainer if you are purchasing new parts.

If you have to purchase a kick start, might as well make that a MK3 type. They give a bit more clearance on the exhaust and a bit more leverage on the engine.
The other good option is a folding RGM kickstart.

My combat goes 120 miles with a steel roadster tank even over Sonora pass at 10,000 ft. But chose the style that suits you then if later it doesn’t change again. I’ve had my roadsters in Interstate and fastback. Both have the longer range advantage and more comfortable seat I still then returned to roadster as that to me is what a 750 should be. It’s light, lean and nimble, a street tracker. 850s should be Interstates.

I don't see much on a kickstart 850 that weighs more than a 750. Maybe a few pounds of frame, crankcase and swing arm strength partially cancelled out by bigger cylinder holes!

Glen

MichaelB said:

FYI, those beautiful cylinder heads and cases you see at CNW and NYC, have probably been Vapor Blasted/ or Honed as some say.

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They’re ‘tumble cleaned’. Some kind of large vibrating vessel full of ceramic beads I believe. There are other places that offer this. It’s a very durable and low maintenance finish as it closes the pores and smooths the roughness of castings, making them much easier to keep clean in use.

I'm with Ken - production racer is good:

https://www.google.com.au/search?q=...AR6BAgHEAE&biw=1920&bih=906#spf=1575426669917

worntorn said:

I don't see much on a kickstart 850 that weighs more than a 750. Maybe a few pounds of frame, crankcase and swing arm strength partially cancelled out by bigger cylinder holes!

Glen

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Not that I believe actual weights advertised, but Norton sales brochures indicate 850s are more than 30 lbs heavier than 750s.
‘72 brochure showing dry weight 385-395. ‘73 brochure says dry weight 418-430. Both with note depending on style.

Can't see anything in the parts books that would create that kind of weight difference on the kickstart bikes.
A few lbs at most.
One day I'll put my friend's 71 750 on the hanging scale.

Glen

Fiberglass vs steel would be part of that.

FG vs steel on the fuel tanks perhaps, although another friend has an all stock 73 850. It came from the factory with a Fibreglass Interstate tank.
Those tanks aren't that light either as the wall thickness is much greater than steel.

Glen

It is very difficult to make a road bike lighter. If the earlier Commandos were lighter, I would be surprised. It is more likely that the bikes would get lighter as the design was improved in later models. Unless cast wheels were fitted to get better handling.

The Commando models did get a little heavier over time as some parts broke, flexed or bent with usage. Norton was made aware of the various shortcomings and made necessary improvements.
I weighed one of the very first flimsy 750 swing arms, a gusseted 850 swing arm and the stiffest of the bunch, the MK3 swing arm. I recall that early to late was about a pound and a half. So you can make things a lot stronger with 10 pounds placed in the right places.
The e start added another 25 pounds.


Glen

Build what you want and slowly source a seat, tank and side panels for the other model (Interstate and roadster). That’s my plan. Once my build is done I’ll be looking for ways to keep up this stupid spending pattern. Or maybe even go whole hog and source proddy racer and JPN bodywork and bars. Kind of like a swatch watch collection only way more expensive and nerve racking to store in the garage.

As for weights, they are listed in the workshop manual. There is very little difference between the models. As for why an 850 might make a better Interstate than a 750, I was always a bit puzzled about a Combat Interstate. It seemed to me that it was a natural canyon runner that should be lightweight and nimble. The 750 typically is viewed as the canyon machine and the 850 the workhorse, whether its true or not. But for quick lane changes and cornering the extra fuel weight could be considered a negative.