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Stainless exhaust collars
Posted: 28 Nov 2025 14:41
by Oli Hulme
I bought one of these to replace a chromed/bronze one that had to be destroyed to remove it. It only screws in about halfway, and then sticks. I've tried on three different heads, and it's the same on each. My remaining Bronze collar screws in just fine. Do the bronze collars wear, making them easier to put in? Or are the thread sizes variable on stainless ones? ~Or are they simply tight because they are new?
All advice gratefully received
Re: Stainless exhaust collars
Posted: 28 Nov 2025 16:51
by George 350
Hi Oli.
It suggests that the thread is not parallel on the stainless nuts. Can you measure the thread diameter at the beginning of the thread and closer to the plain section? This would give you a clue as to why it is jamming.
The other scenario is whether the thread pitch is correct or not. Laying your 2 nuts together and holding up to the light should show if the pitch is correct or not.
Hope this helps,
George
Re: Stainless exhaust collars
Posted: 29 Nov 2025 11:57
by Oli Hulme
well, that nuisance. it appears the stainless one is about half a mil wider than the original. I have a bloody expensive paperweight, then
Re: Stainless exhaust collars
Posted: 29 Nov 2025 14:59
by 3potjohn
Could it be for a 500?
Re: Stainless exhaust collars
Posted: 29 Nov 2025 16:58
by Oli Hulme
are they bigger by that much? It was sold as for a 350
Re: Stainless exhaust collars
Posted: 29 Nov 2025 19:34
by Stempy
From memory 350 are 42mm and 500 are 45mm the castellated head sizes are also different
Re: Stainless exhaust collars
Posted: 30 Nov 2025 10:47
by Stempy
- IMG_1666.jpeg (149.15 KiB) Viewed 297 times
Re: Stainless exhaust collars
Posted: 01 Dec 2025 11:44
by Oli Hulme
the old one is 42mm. the new one is 43mm...
Re: Stainless exhaust collars
Posted: 01 Dec 2025 14:58
by George 350
Hi Oli,
Where did you get the stainless ones from?
The supplier needs to know that they aren't fit for purpose. Can you not return them?
They shouldn't become expensive paperweights for you.
Glad you resolved it without wrecking the head(s).
Good luck and hope you don't have any more surprises on the rebuild and thanks for the publicity you are giving the club.
Regards,
George.
Re: Stainless exhaust collars
Posted: 02 Dec 2025 01:11
by George 350
Another thing Oli,
As an addition to your rebuild, you mentioned in CBG about M7 nuts and bolts.
DW Middleton stainless sell them, in nyloc too.
Perfectly ok for rocker trunnions and brake torque arms on Sports/Stradas. (Bolt only there to hold torque arm in place on welded on collar).
It's only the M7 kickstart bolt that I worry of stainless being strong enough to cope , but they have worked ok for the last 30+years on the Sport so probably are ok!
Regards,
George
Re: Stainless exhaust collars
Posted: 03 Dec 2025 13:14
by norbert
Are you sure, that stainless esxhaust collars are the adequade material to insert in our heads?
I have a brand new pair of them since years. But building up Dulcinea I decided not to use them. Maybe with ceramic or copper paste it will do, but in my opinion this cobination of material is not the best choice
Re: Stainless exhaust collars
Posted: 03 Dec 2025 13:23
by Oli Hulme
George 350 wrote: ↑02 Dec 2025 01:11
Another thing Oli,
As an addition to your rebuild, you mentioned in CBG about M7 nuts and bolts.
DW Middleton stainless sell them, in nyloc too.
Perfectly ok for rocker trunnions and brake torque arms on Sports/Stradas. (Bolt only there to hold torque arm in place on welded on collar).
It's only the M7 kickstart bolt that I worry of stainless being strong enough to cope , but they have worked ok for the last 30+years on the Sport so probably are ok!
Regards,
George
funnily enough, I've just finished off the engine and the kickstart bolt is missing!
I shall pop up to my local fastener people when this edition has gone to press and ask them. I have to get some 2BA screws for the triumph...
I cant remember where i got the collar from. It was years ago!
Re: Stainless exhaust collars
Posted: 03 Dec 2025 13:26
by Oli Hulme
norbert wrote: ↑03 Dec 2025 13:14
Are you sure, that stainless esxhaust collars are the adequade material to insert in our heads?
I have a brand new pair of them since years. But building up Dulcinea I decided not to use them. Maybe with ceramic or copper paste it will do, but in my opinion this cobination of material is not the best choice
tbh i was wondering that myself. I've been using high temp aluminium grease on all the stainless bolts i've been using going into alloy, but that thread on the head looks awfully vunerable. I think i'll search for a proper one, and possibly get this one turned down a mm in the meantime
Re: Stainless exhaust collars
Posted: 03 Dec 2025 16:57
by norbert
I do have some stainless bolts in aluminium as well (fork clamps etc.) Allways screwing them in with mos2-grease. But don't daré this with te delicate exhaust threads.
Re: Stainless exhaust collars
Posted: 04 Dec 2025 19:17
by Oli Hulme
interesting points about Stainless collars, which i had considered (i was going to use aluminum grease) and decent replacements are unobtainable...
I'm now looking at lengths of brass tubing... i could get 100mm 50mm tube with a 35mm inner diameter for about £40 . then i just need a machine shop to cut a thread onto it...