Unbalanced exhaust setup

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WEM

WEM

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The left (drive side) exhaust pipe on my 1974 850 MK II has cracked completely through just outward of the exhaust pipe balance connector. There‘s not much material left. The pipe wall is paper thin. I’m considering replacing the balanced exhaust with an unbalanced setup. From the parts diagrams, it looks like the balanced setup uses the shorter exhaust lockring while the unbalanced pipes use the longer lockring. Are there any other issues I should be aware of when fitting an unbalanced exhaust system to an 850 MK II?
 
Short answer: no other issues. You won't need the collets (06.5260) you currently have but probably should use new sealing washers (06.03995) and you do need the long lockrings (06.2464) like you said.
 
I wasn’t aware of the long/short lock rings until now. I have just removed the balanced set for an unbalanced set and immediately realised a difference in the arrangement without collets. I thought perhaps my exhaust (brand new but 20 years old) may have been faulty, and for now I’ve simply put in an extra gasket and snugged it up, it seems to work for now.
 
I wasn’t aware of the long/short lock rings until now. I have just removed the balanced set for an unbalanced set and immediately realised a difference in the arrangement without collets. I thought perhaps my exhaust (brand new but 20 years old) may have been faulty, and for now I’ve simply put in an extra gasket and snugged it up, it seems to work for now.
 
Fast Eddie said:
I wasn’t aware of the long/short lock rings until now. I have just removed the balanced set for an unbalanced set and immediately realised a difference in the arrangement without collets. I thought perhaps my exhaust (brand new but 20 years old) may have been faulty, and for now I’ve simply put in an extra gasket and snugged it up, it seems to work for now.
Click to expand...
The longer lock rings have the advantage of using more thread depth (well, not ‘more’ just the ‘correct’ designed amount) and are subsequently much kinder on those ex threads in the head, so it’s worth putting them on the TTD list.
 
The engagement difference is 1 mm (0.040") between the two headers.
Some of it is a myth as the balanced header flange is thinner (to make some compensation for the rings) than the non balanced so only that 1 mm difference.
The thread pitch is around 1.8 mm (per turn) so that 1 mm is not much more than a half turn extra.

There is only an 1/8" in the nut thread depth, 5/8" and 3/4".
I am not sure why but the non balanced headers I have, have more muffler kick up than the balanced version but can only assume their mount plates are the same.
 
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You may need to go up one size on your jets if you are running Amal Mk1's. I found that I had to do this when I did the change over from my Siamese Balanced Cross over pipes to the singles and peashooters.
I had 260 mains and I am now running 270's.
YMMV
Cheers,
Tom
 
I use the spherical seats even with the unbalanced pipes, they allow you to get a better angle on the timing side so even with the pre MK3 kickstart you can avoid the clash of kickstart lever on the pipe.
 
CanukNortonNut said:
You may need to go up one size on your jets if you are running Amal Mk1's. I found that I had to do this when I did the change over from my Siamese Balanced Cross over pipes to the singles and peashooters.
I had 260 mains and I am now running 270's.
YMMV
Cheers,
Tom
Click to expand...
How did you confirm you needed more gas on the big end?
 
kommando said:
I use the spherical seats even with the unbalanced pipes, they allow you to get a better angle on the timing side so even with the pre MK3 kickstart you can avoid the clash of kickstart lever on the pipe.
Click to expand...
The MKIII seals (06.5259) and long exhaust lockrings (06.2464)?
 
When I converted my 850 to the OEM balanced pipes from the (OP-installed) individual pea-shooters a few years ago, I didn't change any other parts as far as mounting them. I just took the old header pipes off, put in new gaskets and mounted the balanced pipes. Everything tightened up/sealed appropriately. So I have to say I didn't know there was any difference and, apparently, neither did the bike! :)
 
MexicoMike said:
When I converted my 850 to the OEM balanced pipes from the (OP-installed) individual pea-shooters a few years ago, I didn't change any other parts as far as mounting them. I just took the old header pipes off, put in new gaskets and mounted the balanced pipes. Everything tightened up/sealed appropriately. So I have to say I didn't know there was any difference and, apparently, neither did the bike! :)
Click to expand...
Since the exhaust lockrings cannot be slid on from the rear of the header pipes when there is a balance pipe, that only means that the bike had the balanced pipe hardware before your change.
 
marshg246 said:
The MKIII seals (06.5259) and long exhaust lockrings (06.2464)?
Click to expand...
The MK3 spherical seats but bronze lockrings which are based on the long version, no collet rings. The amount of thread showing suggests short lock rings would work but they are steel not bronze. Even with the large flange on the pipe the ID of the pipe flange rests on the sphere and allows the pipe to move a few degrees.
 
"Since the exhaust lockrings cannot be slid on from the rear of the header pipes when there is a balance pipe, that only means that the bike had the balanced pipe hardware before your change"

Aha! Well, that makes sense since the bike would have had the balanced pipe system originally. So I guess whoever removed the balanced pipe installed the individual pipes using the same OEM balanced pipe hardware.
 
"
The engagement difference is 1 mm (0.040") between the two headers.
Some of it is a myth as the balanced header flange is thinner (to make some compensation for the rings) than the non balanced so only that 1 mm difference.
The thread pitch is around 1.8 mm (per turn) so that 1 mm is not much more than a half turn extra."

I have to diasagree.

1621776459936.jpeg
 
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There are replacement unbalanced '850' pipes available that use the standard short 850 lock rings and collets.

www.thebonnevilleshop.com

Norton Commando 850 MK11A Exhaust Pipe Set Unbalanced PN# 06-3397/8 UN

Norton Commando 850 MK11A Exhaust Pipe Set Unbalanced PN# 06-3397/8 UN For Sale Online With LARGEST SELECTION, FAST, FREE SHIPPING To Lower 48 US, Visit Our Website Https://www.thebonnevilleshop.com/
www.thebonnevilleshop.com www.thebonnevilleshop.com

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 www.feked.com
 
There are also later style (850) finned lock rings with longer threads. I believe they were used on the 73 750's.
 
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