Exhaust Contacts Primary Cover

On my '75 MKIII Roadster: the left exhaust pipe contacts the bottom of the outer primary cover on the flat area adjacent the drain plug. This was true on the pipes I had and on the brand new set of Norton pipes I am now installing. I am hesitant to ding a flat on a brand new set of "Made in England" pipes but if I don't, I am concerned that it may cause stress at the threaded exhaust ports and transfer heat to the primary case. Has anyone been down this road?

Personally I would return the pipe to the vendor, there is not much you can do, and hammering a ding in the pipe is not recomended.
When it comes to replacement exhaust pipes, there is unfortunately a lot of crap on the market.

The original pipes on my MK3 had clearance between them and the primary cover. I had to cut the balance pipe to get them off. I never really like the balance tube anyhow, so tried to replace them with a new set of aftermarket pipes without the balance pipe. That's when I discovered that pre-MK3 pipes have a different bend, and will not clear the drain plug area on the primary cover. I ended up re-using the original pipes with a new balance tube. I do plan to eventually replace them with pipes without the balance tube that will have sufficient clearance, but for now they let me keep riding the bike. I think someone advertises such pipes, specifically designed to work on the MK3, but don't recall who it is.

Ken

Ken,
It's Commando Specialties who sell the non balanced, flared end pipes for Mk 3s, your side of the pond.
sam

Thanks, Sam. Those are the ones I was thinking of.

Ken

Mine has quite the wear mark in the casting. It is behind the drain screw. This was caused by fitting 750 pipes many years ago. I have the original cross over bean can system and it fits well using the 06-5260 collets ,
without touching the outer case. I'll look up these C.S. pipes , did not know there was a solution available.

lcrken said:

The original pipes on my MK3 had clearance between them and the primary cover. I had to cut the balance pipe to get them off. I never really like the balance tube anyhow, so tried to replace them with a new set of aftermarket pipes without the balance pipe. That's when I discovered that pre-MK3 pipes have a different bend, and will not clear the drain plug area on the primary cover. I ended up re-using the original pipes with a new balance tube. I do plan to eventually replace them with pipes without the balance tube that will have sufficient clearance, but for now they let me keep riding the bike. I think someone advertises such pipes, specifically designed to work on the MK3, but don't recall who it is.

Ken

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I have also further researched this matter and I find you and I have reached similar conclusion. Many years ago, circa 1996, an old guru I know told me to use the non crossover 750 pipes. I did this way back then. They also interfered somewhat with the primary but these were aftermarket and I guess I attributed the fit issue with substandard aftermarket fit and I lived with it.... don't really remember. I am doing a lot of work to the bike in 2017 and I ordered another set of 750 pipes and these also interfere at that same location under the primary at the drain plug. These pipes are Andover Norton pipes and for the price I paid, I will not tolerate them rubbing. I contacted my supplier and he indicates, after further research, there is a difference. He had me return the 750 pipes and is ordering a set of non crossover pipes that are designed specifically for the MKIII. I expect these to solve the matter but of course won't know for sure until I have them. You know how Mr Murphy is. Delivery is in Feb. Thanks for your interest in this matter.

It has been known for years that if replacing the balanced MK3 pipes with non balanced pipes that the bend is different, not much, as in most cases 9 times out of 10 there is sufficient clearance near the drain plug. You only need about 1/4'' as the pipe when done up correctly at the head this point will move with the Engine and primary cases so not an issue. Whoever sold you the pipes would have known if you asked them.