Interstate Downpipe Question

I am restoring a June '74 MK2A 850 Interstate and was wondering which downpipes were fitted as standard?

My 74 as built 9/73 and has twin pipes and a balance pipe with black cone end silencers and a pair of pea shooters.

Yorkie said:

I am restoring a June '74 MK2A 850 Interstate and was wondering which downpipes were fitted as standard?

Click to expand...

06.5256 and 06.5257 the same as the 850 Mk3.
https://andover-norton.co.uk/en/shop-drawing/147/exhausts-mufflers-passenger-footpegs
https://andover-norton.co.uk/en/shop-details/20631/exhaust-pipes-pair-850mk3-balanced

Here are a few pictures of the original exhaust pipes from my Mk 2A Interstate built in June 1974 engine #316188. These pipes still used the crushed gaskets unlike the Mk 3 pipes. Also when I compare these pipes to the Mk 3 pipes that Andover-Norton sells, the bottom of my LH pipe that goes underneath the primary chain case is straight while the Mk 3 pipe has a slight curve to it (apparently it needs to clear the Mk 3 primary cover). The only possible identifying mark that I could find on my pipes is the letter F stamped on the outlet end.

With the original exhaust pipes I had replaced the black cap mufflers with standard peashooter roadster mufflers. They fit just fine with the correct adapter plates. So I don't know what the difference is between a Mk 2 and Mk 2A exhaust pipe.

With the original pipes, the rose nuts would constantly loosen. Most frustrating! I have since replaced the pipes with unbalanced exhaust pipes that have the flared end like the 850 Mk 3 exhaust pipes. With these exhaust pipes the loosening of the rose nuts became a thing of the past. I guess the 850 type flared end pipes is an improvement. So if you are planning on buying a new set of balanced exhaust pipes, I would recommend getting the 850 Mk 3 type that L.A.B. mentioned.









Peter Joe

PeterJoe said:

With the original exhaust pipes I had replaced the black cap mufflers with standard peashooter roadster mufflers. They fit just fine with the correct adapter plates. So I don't know what the difference is between a Mk 2 and Mk 2A exhaust pipe.

Click to expand...

Mk2 Roadster and Hi-Rider pipes (for peashooters) were 065464/065465 which suggests there was a difference of some kind to the 'A' pipes?

I seem to remember Paul Bryant of Viking exhausts saying (somewhere?) some while ago that black cap pipes had a different bend to peashooter pipes which splays peashooters more at the rear. My Mk3 with 065256/7 black cap pipes and peashooters I'd say it's probably true although not that noticeable.

The Mk1A pipes were 064202/064203 and I believe they had the collet groove fitting your pipes have. Mk1A had the same black caps as Mk2A and Mk3 (064170)

The Mk2 Interstate had a different low-level exhaust system.

PeterJoe said:

Here are a few pictures of the original exhaust pipes from my Mk 2A Interstate built in June 1974 engine #316188. These pipes still used the crushed gaskets unlike the Mk 3 pipes. Also when I compare these pipes to the Mk 3 pipes that Andover-Norton sells, the bottom of my LH pipe that goes underneath the primary chain case is straight while the Mk 3 pipe has a slight curve to it (apparently it needs to clear the Mk 3 primary cover). The only possible identifying mark that I could find on my pipes is the letter F stamped on the outlet end.

With the original exhaust pipes I had replaced the black cap mufflers with standard peashooter roadster mufflers. They fit just fine with the correct adapter plates. So I don't know what the difference is between a Mk 2 and Mk 2A exhaust pipe.

With the original pipes, the rose nuts would constantly loosen. Most frustrating! I have since replaced the pipes with unbalanced exhaust pipes that have the flared end like the 850 Mk 3 exhaust pipes. With these exhaust pipes the loosening of the rose nuts became a thing of the past. I guess the 850 type flared end pipes is an improvement. So if you are planning on buying a new set of balanced exhaust pipes, I would recommend getting the 850 Mk 3 type that L.A.B. mentioned.

Peter Joe

Click to expand...

Thank you for the tip on the MK3 pipes.

These photos are of a 74' MK II Interstate.

I am about 99% sure its a MK2 and not a MK2A, but some of the issue date stampings still have me curious.

I took these photos (upon delivery) after finding it buried in a barn in Nevada buried underneath a collapsed hayloft for 44 years. I shot the first two pics straight off the delivery truck...all I did was put it on my lift and stare at it for a day.
The mice, goats, horses, coons and rats ate the original seat...the barn owner threw in a Roadster seat as compensation.

The last two shots' don't show it well, but for this issue date there was a crossover pipe when I found it
Mfg. date of June of 74'.

Lineslinger said:

These photos are of a 74' MK II Interstate.

I am about 99% sure its a MK2 and not a MK2A,

Click to expand...

Yes, most likely a Mk2 as the majority of US models were Mk2s and there are no specific '2A' parts on it.

Lineslinger said:

but some of the issue date stampings still have me curious.

Click to expand...

Why?

Lineslinger said:

The last two shots' don't show it well, but for this issue date there was a crossover pipe when I found it
Mfg. date of June of 74'.

Click to expand...

850 exhausts should have a balance pipe.
http://www.classicbike.biz/Norton/Brochures/1970/1973NortonLineUp.pdf
http://www.classicbike.biz/Norton/Brochures/1970/74NortonBrochure.pdf

The Mk2 Interstate had a different exhaust system to Mk2 'peashooter' models (Roadster, Hi-Rider).
https://andover-norton.co.uk/en/shop-drawing/78/850-exhausts-muffler-mutes-passenger-footpegs

Lineslinger said:

View attachment 15280 View attachment 15281

View attachment 15282 View attachment 15283

Click to expand...

The 'Mk2A/Mk3' type flared exhaust pipes with spherical seatings do not use crush washers.