documentary- exhaust thread repair

[comnoz]

Wit stock aluminum threads there is probably a small advantage in using the bronze nuts because they expand at a rate similar to the aluminum head so they tend to stay tighter. With the bronze inserts I would stay with steel nuts to avoid the friction caused when like metals rub against each another.
An interferance fit means the insert is slightly larger than the hole it is being screwed into when they are at the same temperature. To make it fit I heat the head and cool the insert before I thread them together. Locktight sets up very fast when it gets hot . Sometimes faster than I could screw the insert into the hole. Then I ended up having to bore out a half installed insert that wouldn't move anymore and starting over. There is no such thing as overkill when it comes to keeping an exhaust attached to a Norton head. Jim

Is there a reason why you prefer an interference fit and JB weld rather than key locking ?

Yes, It's because I have seen a few heads that had key locking show up with cracks starting at the thin section next to the key. I have had no problems with the inserts coming out with-out the key. Jim

 

[swooshdave]

.. There is no such thing as overkill when it comes to keeping an exhaust attached to a Norton head. Jim

I agree , but then why not fix them like this :

I would consider that a mod rather than a fix. Especially when you have to use non-stock pipes for that to work (I assume).

 

[Jeandr]

.. (I assume).

You assume wrong .
Call it a mod if you like , but it is a much better way to fix the pipes than the STD setup .

If I am not mistaken, ALL modern motorcycle exhaust pipes are held with studs and nuts, not to mention all car exhausts and they never come loose or cause damage to the heads. I'm with Ludwig, it's a much better way than the original.

Jean

You can see a cyclist with bags, must have been quite a ride to get there.

 

[splatt]

.

Jean

You can see a cyclist with bags, must have been quite a ride to get there.[/quote]

Mail delivery?????

 

[lcrken]

I have to agree with ludwig and Jeandr that the studs and nuts are now the common technique, and maybe mechanically "better" (or maybe not). Like all mods, it comes down to the owner's personal taste in what his Norton should look like. I just like the look of the original finned rings better. Sort of like my feelings about the cast, finned rocker covers. They might be better, but I still like the look of polished originals better. I'm certainly not opposed to modifiying my Nortons, obviously, but there are some original features that just seem to not look right to me when changed. It's strictly a cosmetic issue.

Besides, what would I do with all those special Norton exhaust nut wrenches if I changed to studs?

Which reminds me of another story. Years ago someone sold the exhaust nuts in aluminum, so I immediately bought a pair and tried to install them. I used the stock Commando wrench to tighten them. Big mistake. I think I still have them somewhere in a box, with the broken fin from one. They probably would have seized in the head anyhow.

Ken

 

[Rich_j]

Which reminds me of another story. Years ago someone sold the exhaust nuts in aluminum, so I immediately bought a pair and tried to install them. I used the stock Commando wrench to tighten them. Big mistake. I think I still have them somewhere in a box, with the broken fin from one. They probably would have seized in the head anyhow.

Ken

I've been there as well and yes they do seize in the head, part of the finned ring snapped off with the collar part way out :cry:

 

[comnoz]

.. There is no such thing as overkill when it comes to keeping an exhaust attached to a Norton head. Jim

I agree , but then why not fix them like this :

Partially because I don't like to weld on a Norton head unless it is the only way to save it. No matter how correctly the weld is made or how acomplished the welder the heat treat on the head is affected . The head will not have the strenght after welding that it did to begin with. I see no problem, if the weld is small and away from the bulk of the metal such as on the fins but when you weld to the thicker sections there is no way to avoid heating the head to strength damaging levels. I have rebuilt many heads that had the aluminum exhaust thread insert welded in down at the bottom of the insert instead of around the outside edge. When I need to ream the guide holes oversize because the guides came loose I usually find the aluminum around the exhaust guide is like machining chewing gum. It is partially annealed and does not cut cleanly. Welding them in around the outside edge doesn't seem to affect the hardness much but it doesn't look very good.
I have also found that when the bronze inserts are installed and the thread fit is much better than they were when they came from the factory, then the exhaust nuts don't have a tendency to come loose. Jim

 

[swooshdave]

Jim ,
I agree with what you say about welding on heads , but to install the studs , only minimal welding is required to add some material at the 4 corners .
I made bronze inserts like yours too , but they need very precise machining .
(I can't cut the thread in the ports , so I had to have that done by a machine shop )
The alloy flanges to hold the pipes are much easier to make and not at all critical .
In all , I think the solution with studs is easier and cheaper :
a little welding , threading , brass studs and copper exhaust nuts ..
only very little tension is needed on the nuts to hold the pipes in place , and they will never come loose .
If you have to put time and money in arepair it anyway , why not go for a technical superior solution ?
But if someone absolutely wants the look of oriiginal .. I can' argue with that .

Where do you get the plates to hold the pipes on? Are they custom or from another bike?

 

[swooshdave]

..Where do you get the plates to hold the pipes on? Are they custom or from another bike?

They are custom made .No big deal if you have a lathe .

CNW has the exhaust port fix for $157 each side. For someone who doesn't have a lathe or mill that is a heck of a deal.

For your solution you would need a lathe and a welder, probably a mill too. And pay someone to use those tools. And will be almost as effective as the four bolt approach.

 

[swooshdave]

..For your solution you would need a lathe and a welder, probably a mill too..

If you read this thread from the beginning , You 'll see that my reply was to the original post of Jim Comstock ..I believe Jim has a lathe ?

Jim can do anything he wants with metal, the rest of us may not have that luxury. Jim developed his inserts for the rest of us, not just for himself. For which this is a great solution.

 

[comnoz]

Ludwig said ..
I believe this lies within the possibilities of many hobby tinkerers , like me .
only very little tension is needed on the nuts to hold the pipes in place , and they will never come loose .
If you have to put time and money in a repair anyway , why not go for a technical superior solution ?
But if someone absolutely wants the look of oriiginal .. I can't argue with that .


I would have to agree that your repair is likely to be cheaper and easier for a DIY'er to complete with moderate equipment. I am not so sure about studs being superior as I have fixed my share of broken off studs too.
Working with aluminum bronze requires some pretty serious tooling. Any carbide bit that has ever touched another metal is no longer usable on al. bronze so it requires dedicated tooling. Not generally for the tinkerer. Jim

 

[Hortons Norton]

I really like the idea that there is more than one way to skin a cat, If you are one of those guys that just can't have anything on his bike that is not original Jim's way is the cat's meow, It will maintain the total stock look and work much better than stock. If you want to totally scratch the problem of the original nuts coming loose off your list, Then Ludwig's way seems to be the purrr-fect way to go. And then you can throw that 3 pound wrench in the bin. That's what I find so fun about owning old bikes, You always have things to tinker with. Both ways to repair it are great in their own way, It's just that I wish I had the tools and the know how to do the same. Keep up the GREAT work guys, We can always use fresh idea's to keep these machines purrrrrring! Ride safe, Chuck. Hey Ludwig, It looks as if the snow has melted? Is that why the bikes apart? I know you love to ride in the snow. :wink:

 

[seaguy]

Use 2 studs and a CB honda exhaust nuts setup. Voila! studs and nuts wi fins :lol:

 

[Onder]

Just read the whole thread through and must say that it
made me laugh to see the studs and nuts. In small
aircraft repair, those nuts either seize or fall off. If
they seize, the studs then come out. So your repair
is to go to stock and get an oversize stud. They
come in several oversizes. This is a common
problem.
Never had problems with the Trident spigots!