Exhaust pipe replacement

rdleeart · May 16, 2016

Hi. I recently purchased a pair of the Commando Specialties Norton 850 commando pipes to replace my old balanced exhaust. The flanges on the new pipes are slightly larger than the old pipes, meaning that the exhaust nuts must slide over the pipe up to the flange. This, of course, implies that the split collets used in the original setup may not be necessary to seal the pipe into the conical seat since the exhaust nut seats against the flange quite nicely.

So, I have a couple of questions.

If I leave the split collets out, the exhaust nuts are pretty close to making contact with the head and I haven't really horsed them down all the way. If I put the collets in, I'm showing about an 1/8" of threads which I would prefer being used to keep the nut tight.

The way I see it I have a couple of options. Use the collets or put a crush washer behind the conical seat. From what I have seen on the forum, I am leaning towards using the crush washers. Anybody have any opinion or alternatives? Praise be to the gods of the machine, the threads look like they're in good shape so I want to keep them that way. Thanks for the help.

comnoz · May 16, 2016

The right way to do it would be to buy the earlier "long" nuts that went with the earlier style pipe that your using.
The "short" nuts that were used with the collets did not give as much thread engagement. Jim

rdleeart said:
Hi. I recently purchased a pair of the Commando Specialties Norton 850 commando pipes to replace my old balanced exhaust. The flanges on the new pipes are slightly larger than the old pipes, meaning that the exhaust nuts must slide over the pipe up to the flange. This, of course, implies that the split collets used in the original setup may not be necessary to seal the pipe into the conical seat since the exhaust nut seats against the flange quite nicely.

So, I have a couple of questions.

If I leave the split collets out, the exhaust nuts are pretty close to making contact with the head and I haven't really horsed them down all the way. If I put the collets in, I'm showing about an 1/8" of threads which I would prefer being used to keep the nut tight.

The way I see it I have a couple of options. Use the collets or put a crush washer behind the conical seat. From what I have seen on the forum, I am leaning towards using the crush washers. Anybody have any opinion or alternatives? Praise be to the gods of the machine, the threads look like they're in good shape so I want to keep them that way. Thanks for the help.

Danno · May 16, 2016

Isn't it either/or with the conical seals and crush washers? I am running the conicals only with no leakage.

comnoz · May 16, 2016

Danno said:
Isn't it either/or with the conical seals and crush washers? I am running the conicals only with no leakage.

The conical seats were originally used with a pipe with a taper flared end . They would probably seal when using a pipe with a flat end but I have never tried it. Jim

concours · May 17, 2016

As mentioned, Collet halves are only for use with crossover equipped pipes. You'll need the longer nuts.
engineering-compromises-leading-exhaust-threads-stripped-t14363.html

L.A.B. · May 17, 2016

rdleeart said:
Hi. I recently purchased a pair of the Commando Specialties Norton 850 commando pipes to replace my old balanced exhaust. The flanges on the new pipes are slightly larger than the old pipes, meaning that the exhaust nuts must slide over the pipe up to the flange. This, of course, implies that the split collets used in the original setup may not be necessary to seal the pipe into the conical seat since the exhaust nut seats against the flange quite nicely.

Why didn't you buy their 850 Mk3 pipes? :?

http://commandospecialties.com/norton-e ... pipes.html

Made specially for the MKIII to clear the larger primary cover

Biscuit · May 17, 2016

I think most of you are missing the point of the question. rdleeart IS replacing a balanced exhaust system, so it would have had conical washers, along with split collets, with a non balanced system, but still with conical washers. So it will mount the same including the correct exhaust nuts. The question as I understand it, is because the bells are larger than the original, the nuts will bear directly on them without the apparent need for the collets. He has all the correct parts but the concern is that with the collets the nuts will not have as much depth into the head.

To rdleeart: I understand your concern about the shallower nut depth but also consider that without the collets. the nuts will have to be tightened directly against the relatively thin wall of the pipe bell itself and I think there can be potential to damage them. The collet system allows for even pressure against the bell and the nut does it's twisting against them.

dynodave · May 17, 2016

750 system
850 system 73-74 balanced straight collets
850 MKIII balanced flared collets
aftermarket flanged
aftermarket flared pipe/conical seat no balance

He must have a MKIII (conical seat) ??
Did he get a long LH pipe or will it bang on the bottom of the MKIII primary?

rdleeart · May 17, 2016

I should have been a little more clear. Biscuit is correct, I did get the 850 MKIII pipes that have the flared flange like the old balanced pipes, the difference being the size of the flange. It's larger and the nut must go over the pipe unlike the balanced pipes which have to go over the flange itself. The new pipes do not have the flat flange that were used in the earlier models. I have the conical seals which is what my new pipes fit.

I think you may be right Biscuit. The collets probably will be less damaging to the thin wall of the pipe. I will install and tighten them up to see how far the nuts thread in and report back. Thanks for all the input guys.

jimbo · May 17, 2016

dynodave said:
750 system
850 system 73-74 balanced straight collets
850 MKIII balanced flared collets
aftermarket flanged
aftermarket flared pipe/conical seat no balance

He must have a MKIII (conical seat) ??
Did he get a long LH pipe or will it bang on the bottom of the MKIII primary?

note, I used the preMK111 balanced type with a flat pipe end on my MK111 with no left side interference

dynodave · May 19, 2016

jimbo said:
dynodave said:

750 system
850 system 73-74 balanced straight collets
850 MKIII balanced flared collets
aftermarket flanged
aftermarket flared pipe/conical seat no balance

He must have a MKIII (conical seat) ??
Did he get a long LH pipe or will it bang on the bottom of the MKIII primary?

Click to expand...

note, I used the preMK111 balanced type with a flat pipe end on my MK111 with no left side interference

You are either very lucky to get a longer than normal 73-74 pipe OR you have problem getting to the drain plug OR the pipe is swung out of position. Your "fits correctly" situation is definitely abnormal based on the many MKIII i have seen or worked on.

jimbo · Jun 13, 2016

must be my luck!

Exhaust pipe replacement

rdleeart

comnoz

Danno

comnoz

concours

L.A.B.

Moderator

Biscuit

dynodave

rdleeart

jimbo

dynodave

jimbo

Attachments

Similar threads