New Owner

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Jun 2, 2008
Hello, New owner of 1975 MkIII Interstate. Beautiful condition but original except for Boyer. First thing I want to do is improve front brake. Any advice on best way to do that since there are no recognized Norton expert techs within 150 miles of me that I know of. Next I want to reconnect the starter and see what needs to be done to make it functional. I was thinking of a Dyno Dave starter with Pazon ignition--after reading numerous posts. Is this the best way to go now? I look forward to having some fun and learning a lot. Never had a British bike before, let alone a Norton. All info appreciated. Rick
Welcome Rick,

There are various options available to upgrade the brake including larger diameter disc and caliper kits.
Some owners (like myself) find that resleeving the master cylinder to 13mm and fitting a stainless braided brake line and better pads is a definite improvement compared to the original brake setup.

My MkIII starts easily on the electric starter (far easier than kicking it) and runs fine with a Boyer*, contrary to popular opinion! However the Pazon is a more technically up to date electronic system.

The Dyno Dave starter is a worthwhile upgrade, but the Prestolite starter can be made to work quite well if a powerful enough battery is used, with heavier gauge starter leads and the four-brush conversion. One weak point in the starter system is the sprag unit which can break. If you have the old 14 element sprag unit then I suggest you change it for the later 18 sprag type.

* I did replace the Boyer with a more modern Tri-Spark system, however I have now refitted the Boyer.
I had RGM to resleeve the master cylinder and used it with a restored original caliper, new hose and pads. In my opinion it provides a good front brake for a reasonable amount of money spent.

As for improving Norton's front disc, which is a horrible excuse for a brake, the best route is the Brembo setup; master cylinder, caliper, floating 12" rotor.

I see is selling the complete kit for $1095. Not bad, when you consider your very life depends on the ability to stop. Years ago I went a cheaper route. has a 12" floating rotor. I also used a Grimeca 2 piston caliper from them. Got a stainless steel braided hose with a 11mm master cylinder from a MZ 250. The reason I went with 11mm is it gave me a ratio of 27:1 between caliper and master cylinder. This is the ratio that calls the sweet spot. The MZ master cylinder also has a brake light switch and mirror mount. I matched it up with the MZ clutch lever. This gives me a great front brake, although the Brembo is probably superior.
Yellow_Cad said:
L.A.B. did you have a problem with the Tri-Spark system?

For some reason I could never start my MkIII from cold using the kickstarter with the Tri-Spark installed? But it would fire up immediately on the electric starter! I may fit the Tri-Spark on my Bonneville and see if it works any differently, and no electric start on that, so it would have to! Maybe I should have asked Steve Kelly what he thought?

Edit: The information above refers to the pre-Classic Twin sequential Tri-Spark EI.
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Hey L.A.B. Where did you get the 18 sprag unit? I am about to dig into the primary in the next few weeks. :?:
Regarding the front brake, check with if you don't want to go the route of the full expensive upgrade from Colorado Norton Works. They're in Sonora, not too far from where you are. They can re-sleeve your stock master cylinder to 13mm. I would also recommend the Ferodo Platinum pads, Vintage Brake has them. A braided stainless brake line will help as well. I've done all this plus a 12" disc from Norman Hyde (probably not available anymore). The brake performance is vastly improved, but definitely not the one or two finger braking that you get with modern bikes. If you want that, you should seriously consider the CNW system.

If you put a modern high performance braking system on your bike, you should also consider a fork brace. There was a previous thread on this forum about using a fork brace to stablize the fork tubes. Aggressive use of a modern braking system on the Commando could tweak the fork tubes.
I had Fred Eaton from Old Britts do his "full monty" upgrade on my front brake - drill and blanchard grind front disc, new pads, s/s brake line, and rebuilt master cylinder. About $750 I believe it was. Brake is a one or two-finger stopper now. Well worth it.
I was in your position a year ago - bought a Mark III, but in my case, since it had been sitting mostly unused for years, both brakes were completely shot.

The seals in both master cylinders were done, fluid was leaking out of the front and rear master cylinder, and the rear caliper was seized.

I had to spend some coin on new mufflers, seat, and other things to make the bike look nice and presentable, and i ended up justifying to myself that I would be OK with "Just Enough" spent on the brakes.

l had the rear caliper rebuilt by OldBritts, and bought the rebuild kits for both master cylinders. When I opened up the master cylinders to install the new seals from the rebuild kits, i realized the pistons were badly corroded. But with a little rationalization, I convinced myself it would be ok with some cleaning up of the pistons, plus the new seals.

I put new pads on at the same time - but the end result was to almost get the brakes back to the condition when the bike was new. A few weeks ago, I realized how inadequate this is, as I slammed into the back of a Honda Accord which had stopped suddenly in front of me. (I would have been able to stop in time with one of my other, modern, bikes).

I have since gone the route of stainless lines, and had the front MC resleeved (OldBritts).

However, I am still not satisfied with the brakes.

Moral of the story - put your coin on this upgrade and DIRTFT! (Do it right the first time).

PS - my Mark 3 has a kick start lever, but I think i have used it once in a year - the electric start works perfectly.


Were you injured? I certainly hope not.

Moral of the story - put your coin on this upgrade and DIRTFT! (Do it right the first time).

That's some sage advice. Brakes and tires are asolutely no place to compromise. Spend like your life depends on it, because it does.
Wow! Thanks

Thank you all for the great response to my questions. I just got back into Fresno with the bike in the back of a pickup. It looks nice. From cold, it started on the first kick! I think the Amals have been sleeved already. I'm going to contact Vintage Brake in the morniong. I have a friend going up there next week and he can deliever the cylinder for sleeving and bring back the parts they recomend(lines, pads, etc). Then , when the brakes are ok I'm going to hook up the starter and see what happens. It has a new battery that's much stronger than the stock one so the starter may work. I'll get some heavier cables before I try it. If it doesn't work I'll try and see what exactaly the problem is. Maybe with a Dyno Dave starter I won't need the sprague replaced. The fellow who sold the bike said that he disconnected the starter about twenty years ago when he got the bike when the battery just woudn't turn the starter sufficiently to start. He said there were no strange sounds, which leads me to believe the sprague is not tweeked-if I understand the problem. He says the Boyer doesn't cause any kick backs. We'll see how it goes. Thanks again for the advice. Let me know if I'm misunderstanding some of this stuff. I am not the world's greatest mechanic-maybe the worst! Rick
Re: Wow! Thanks

dfndr said:
Maybe with a Dyno Dave starter I won't need the sprague replaced.

Unfortunately the sprag units tend to disintegrate, and fitting the DD starter won't return your sprag unit to "as new" condition.

However, if the sprag is still in good condition because it hasn't been used all that much in the past, then you could continue to use it? Norvil recommends that all three sprag clutch parts should be replaced (and they won't offer a warranty on the sprag otherwise) which starts to get expensive, so I do suggest you inspect the old sprag cages for cracks first before using it.

When it breaks this can be the result:

New Owner

It is also worthwhile to check that the slip torque of the starter drive overload backfire device is correctly set, as that will save the sprag from being overloaded if there is a kick back. My sprag shown above, broke not that long after I bought the bike, and when I checked the overload device it had been over-adjusted so that it was locked solid!

Some useful Mk III starter information:
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