850 Mk3 exhaust questions (2014)

What silencers are you fitting, if replacing blackcaps with peashooters the carb main jets need changing from 230 to 260.

I have fitted flanged pipes and spherical seats and it works as it allows more movement on the pipes so clearance to the primary may not be an issue.

Do the pipes up if the head pipe is still a little lose then add another crush washer and everything will be right, I got my header pipes made up when I coverted to the Featherbed frame back in 1980 and using the 850 flangers, I been using 2 crush washers ever since and have never had any leaks or problems with the flangers coming lose in the 41 years set up this way.

L.A.B. said:

You will need to check the fit, as I mentioned, '750' pipes used a slightly longer threaded lockring although you can fit two crush washers or I believe although not standard, you can use the spherical seatings with the flanged pipes. Also, check the LH pipe clears the 850 Mk3 primary chaincase.

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Thanks for the info. I checked the fitment, the using the spherical seatings worked best with the pipes. The LH pipe clears the primary chain case thank gawd. I saw on youtube somewhere where the guy did use 2 crush washers but don’t know if I trust that.

seoulshakers said:

Thanks for the info. I checked the fitment, the using the spherical seatings worked best with the pipes. The LH pipe clears the primary chain case thank gawd. I saw on youtube somewhere where the guy did use 2 crush washers but don’t know if I trust that.

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I have used two just fine.

gortnipper said:

I have used two just fine.

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So just 2 crush washers on each side nothing else? I bought the brackets to fit peashooters one my 75 mk3 that originally had the bean cam mufflers but looking at it, the original bracket looks like it’ll work just fine. The new brackets came in 3 pieces and couldn’t for the life of me figure out how to use it. Did you buy new brackets?

seoulshakers said:

So just 2 crush washers on each side nothing else? I bought the brackets to fit peashooters one my 75 mk3 that originally had the bean cam mufflers but looking at it, the original bracket looks like it’ll work just fine. The new brackets came in 3 pieces and couldn’t for the life of me figure out how to use it. Did you buy new brackets?

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No, this is not.in respect to installing different muffler types. You still need the right hangers.

I have used two crush washers to get the correct seal/gap on peashooter headers and also a Maney style exhaust.

seoulshakers said:

I bought the brackets to fit peashooters one my 75 mk3 that originally had the bean cam mufflers but looking at it, the original bracket looks like it’ll work just fine.

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As you have the peashooter brackets then I suggest you use them.

seoulshakers said:

The new brackets came in 3 pieces and couldn’t for the life of me figure out how to use it

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LH bracket assembly for black caps/bean cans...


LH Peashooter plates. Outline of black cap plates shown for comparison. Fit the large plate on the inside and small plate on the outside of the Z-plate with the original spacer (06-0471, not shown) and AV mounts as below...

Attach the diamond shaped plate to the peashooter, then fit it onto the AV mounts.

L.A.B. said:

As you have the peashooter brackets then I suggest you use them.


LH bracket assembly for black caps/bean cans...

LH Peashooter plates. Outline of black cap plates shown for comparison. Fit the large plate on the inside and small plate on the outside of the Z-plate with the original spacer and AV mounts as below...

Attach the diamond shaped plate to the peashooter, then fit it onto the AV mounts.

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Wow amazing. This is exactly what I needed. Thank you so much!

well aligned everything and had all the bolts nad nuts on loosely but it looks like once I mount the muffler on the left side, the LH is basically touching the primary chain case. I'm trying to look back on the forums to see if there was a fix for but couldn't find it. Anyone run into this issue and figure out a solve? The right side went on smoothly with no issues.

kommando said:

What silencers are you fitting, if replacing blackcaps with peashooters the carb main jets need changing from 230 to 260.

I have fitted flanged pipes and spherical seats and it works as it allows more movement on the pipes so clearance to the primary may not be an issue.

Click to expand...

I initially used the spherical seats with the headers but the clearance is really close to the primary chain case. I did all the combos, spherical, spherical with gasket, 2 gasket and all of them still has the left header very close to the primary chain case.

seoulshakers said:

I initially used the spherical seats with the headers but the clearance is really close to the primary chain case. I did all the combos, spherical, spherical with gasket, 2 gasket and all of them still has the left header very close to the primary chain case.

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Yes, as I mentioned previously, they're not the correct pipes for an 850 Mk3 so the LH pipe isn't bent to clear the Mk3 primary case.

L.A.B. said:

Yes, as I mentioned previously, they're not the correct pipes for an 850 Mk3 so the LH pipe isn't bent to clear the Mk3 primary case.

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Is there any work around this or am I shit out of luck?

seoulshakers said:

Is there any work around this or am I shit out of luck?

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Unless you try to re-bend or dent the pipe (or grind the primary case, personally I wouldn't) then I can't think of any other way except exchange the pipes for the correct Mk3 items (either with or without the balance pipe).


I don't know what you ordered but you have basically been sent the wrong pipes for a Mk3 and the supplier should have been aware of that as it is a known problem.

L.A.B. said:

Unless you try to re-bend or dent the pipe (or grind the primary case, personally I wouldn't) then I can't think of any other way except exchange the pipes for the correct Mk3 items (either with or without the balance pipe).
I don't know what you ordered but you have basically been sent the wrong pipes for a Mk3 and the supplier should have been aware of that as it is a known problem.

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I ordered the non balanced pipes and mufflers from commando specialties. I made sure to tell them I have a 75 mk3

seoulshakers said:

I ordered the non balanced pipes and mufflers from commando specialties. I made sure to tell them I have a 75 mk3

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In that case, I suggest you get CS to exchange them (at their expense) for the correct flared-end non-balanced Mk3 pipes.
Examples:

L.A.B. said:

In that case, I suggest you get CS to exchange them (at their expense) for the correct flared-end non-balanced Mk3 pipes.
Examples:

Exhausts :: Norton :: Exhaust Pipes :: 850cc :: Norton Commando 850cc MK3 Exhaust Pipes Set - WITHOUT Balance

Norton Commando 850cc MK3 Exhaust Pipes Set - WITHOUT Balance. Complete set of pipes to fit a MKIII Norton Commando. 2 pipes without balance. Outlet Size: 1+3/8 inch (35mm). OEM: 06-5256, 06-5257. Chrome plated - made in England

www.feked.com

Norton Commando 850cc MK3 Exhaust Pipes Unbalanced 1975

Norton Commando 850cc MK3 Exhaust Pipes Unbalanced, O.E.M: 06-5256, 06-5257 Outlet size: 1.3/8''

www.classicbikeshop.co.uk

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Thanks for the heads up. I will give them a ring tomorrow. Very frustrating

A little update on my situation. So just like everyone has said, these are the incorrect headers for my bike. LF Harris makes 2 sets of pipes for the 850. #721-N63/B is the part number for 1974 - earlier 850's with the flanged pipes and #721-N63/A is the part number for 1975 - newer 850's with a flared pipes. Why Commando Specialties sent me the wrong ones I have no idea. I called them and explained the situation to them. They didn't seem to know there were 2 types of pipes that LS Harris made so they called their distributors to confirm. They got back to me and confirmed they had the correct ones for me and would send them out and exchange the ones I have.

A lot of back and forth and honestly the only way I was able to get this confirmation was by calling up British Cycle Supplies and they explained everything to me. Definitely going to start my parts search with British Cycle Supplies first before anywhere else. Mark was absolutely amazing there and gave me the help I needed even though I had bought my product somewhere else. Now thats amazing customer service.

I'll report back once I receive the correct headers and start fitment. Hope this helps someone out there.

seoulshakers said:

LF Harris makes 2 sets of pipes for the 850. is the part number for 1974 - earlier 850's with the flanged pipes and #721-N63/A is the part number for 1975 - newer 850's with a flared pipes.

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Actually, #721-N63/B is the flanged 750 pipe set that would normally use the long '750' lockrings so you may have to either double-up on the crush washers or fit your 'short' 850 lockrings with the collets (if they will fit?) and crush washer, because, due to the 850 models having the balance pipe each lockring can only be fitted over the head end of the pipe so the end flange could not be used, therefore, collets, a shorter lockring and grooved end fitting (pic below) were used on the pre-flared 850 pipes so there should really be three sets of pipes, 750, pre-flared 850 and flared 850.



750
850 (Mk2A is not entirely correct)
Mk3 (also late Mk2A)

L.A.B. said:

Actually, #721-N63/B is the flanged 750 pipe set that would normally use the long '750' lockrings so you may have to either double-up on the crush washers or fit your 'short' 850 lockrings with the collets (if they will fit?) and crush washer, because, due to the 850 models having the balance pipe each lockring could only be fitted over the head end of the pipe so the end flange could not be used, therefore, collets, a shorter lockring and grooved end fitting (pic below) were used on the pre-flared 850 pipes so there should really be three sets of pipes for 750, pre-flared 850 and flared 850.

750

Exhausts :: Norton :: Exhaust Pipes :: 750cc :: Norton Exhaust Pipe Commando Roadster 750cc 1970-73

Norton Exhaust Pipe Commando Roadster 750cc 1970-73 OEM: 06-3375, 06-3376 British made classic motorcycle exhaust system

www.feked.com

850 (Mk2A is not entirely correct)

Exhausts :: Norton :: Exhaust Pipes :: 850cc :: Norton Commando 850cc MK2A Exhaust Pipes Set - WITHOUT Balance

These will fit the Norton Models: Commando MK2A 850cc OEM: 06-3397, 06-3398 This is a complete set of two exhaust pipes required to fit a MKIIA Norton Commando. 2 pipes without balance - 2 single pipes only. Exhaust Pipe Dimensions: Inlet Size: 1+5/8 inch

www.feked.com

Mk3 (also late Mk2A)

Exhausts :: Norton :: Exhaust Pipes :: 850cc :: Norton Commando 850cc MK3 Exhaust Pipes Set - WITHOUT Balance

Norton Commando 850cc MK3 Exhaust Pipes Set - WITHOUT Balance. Complete set of pipes to fit a MKIII Norton Commando. 2 pipes without balance. Outlet Size: 1+3/8 inch (35mm). OEM: 06-5256, 06-5257. Chrome plated - made in England

www.feked.com

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They're sending me 721-N63/A with the flared ends where you need the collets and spherical seating. Thanks for sending those Feked.com links. If I ever need new pipes again I'll take a look.

seoulshakers said:

They're sending me 721-N63/A with the flared ends where you need the collets and spherical seating.

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Yes, what I should have said was anyone thinking of fitting the #721-N63/B set to a pre-Mk3 850 would have to do so.