Exhaust nuts and expansion

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Well, I've got two 850 heads; and RH4 and RH10. The RH4 has thread inserts by Jim (Comstock) a while back. The RH10 has steel inserts ... not sure who ever did it, but it looks to be a really good job. For the RH10, to avoid "similar metals galling"; what exhaust nuts are recommended?

BTW, I thought about having these RH10 "steel inserts" redone by Jim, but they really do look like a high quality job; it's just that their steel.
 
much the same here and 40,000 miles with no issues. also has original threads.

Nater_Potater said:
I had Jim add his beautiful aluminum-bronze inserts to my '74 after someone had already done a botched insert job years ago, installed the stock iron nuts using anti-seize compound, leaned on them hard with a 24" tool when cold, repeated once hot, then at the next couple of fuel fill-ups. After a couple of those, the wrench no longer moved (no, they weren't seized...), and they've remained like that for close to 10,000 miles. No springs; no lock tabs; 25 miles a day on the freeway. I checked them a couple times after, but nothing since the initial bedding-in. I'm happy, to say the least!

Nathan
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For any doubters about applying heave ho to the exhaust nut ,here is a mental experiment ... how long if you unwind it would be the thread on say a crankcase stud ? It takes 25ft lb. Now ask how long the thread on an exhaust nut is in comparison ? Granted the metallurgical conditions may not be strictly comparable - but there would still seem to be quite a safety margin . Perhaps some one more mathematically gifted than me could work this out?
 
nortriubuell said:
Well, I've got two 850 heads; and RH4 and RH10. The RH4 has thread inserts by Jim (Comstock) a while back. The RH10 has steel inserts ... not sure who ever did it, but it looks to be a really good job. For the RH10, to avoid "similar metals galling"; what exhaust nuts are recommended?

BTW, I thought about having these RH10 "steel inserts" redone by Jim, but they really do look like a high quality job; it's just that their steel.
Click to expand...

I don't think you will have a problem with any kind of nut in those.

I started out making my inserts out of steel 25 or 30 years ago. It worked fine but always made a ring of rust around the exhaust.
I had to lock them in place with a pin or they would come loose eventually.
 
Two thoughts. First, the gaskets compress owith vibration and heat cycling over time. Second there is no other support for the head pipe except at the Z plate/rubber hanger and each hanger is an axis for the leverage weight of each muffler. That force also compresses the gaskets.

I made a couple of steel support straps that are welded to the bottom of each head pipe and are then bolted to the engine at the front isolastic unit. The brackets are similar to what we see on many other bikes. This reduces the leverage that each muffler has on it’s exhaust nut.

Downside is if I want to change nuts, I can’t because they are now trapped between the exhaust flange and my welded on bracket. I installed new nuts before I welded on my steel head pipe brackets.

There is a heat sink paste that protects the pipe’s chrome from blueing due to the heat of welding.
 
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Two thoughts. First, the gaskets compress owith vibration and heat cycling over time. Second there is no other support for the head pipe except at the Z plate/rubber hanger and each hanger is an axis for the leveraged weight of each muffler. That force also compresses the gaskets.

I made a couple of steel support straps that are welded to the bottom of each head pipe and are then bolted to the engine at the front isolastic unit. The brackets are similar to what we see on many other bikes. This reduces the leverage that each muffler has on it’s exhaust nut.

Downside is if I want to change nuts, I can’t because they are now trapped between the exhaust flange and my welded on bracket. I installed new nuts before I welded on my steel head pipe brackets.

There is a heat sink paste that protects the pipe’s chrome from blueing due to the heat of welding.
 
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Silicone on the threads works to keep out corrosion and helps prevent seizure, it provides a cushion between the threads if the nut loosens and gives you more time before things destroy themselves, also helps prevent the nuts from turning on its own.

There is another advantage with getting rid of the flange on the pipe and holding in the (sleeved) pipe with a spring. If you leave out the washers then you can screw in the nut till it bottoms out in the threads. The O.D. at the end of the nut ramps up into the aluminum and you have a stronger fit because there is no free play in the threads. Less likely to loosen.
 
MZ250's & 300's also have rubber mounted engines which jump around a lot at tickeover. They have a threaded sleeve nut as well, but in addition the downpipe is wisely secured to the engine by the extended silencer clamp which also bolts to the engine and relieves the stress on the thread at the exhaust port. If that clamp isn't tight you can suffer the same fate, but luckily you can normally hear it ( even above the ding-da-da-ding of the MZ at idle).

I like concours simple solution (not contours (no disrespect intended)) here..

https://www.accessnorton.com/Norton...es-leading-to-exhaust-threads-stripped.12653/


Cheers,

cliffa.
 
I said it before , but these exhaust nuts should be tightened with running engine .
Rev it to 4000 rpm and apply a constant pressure on the wrench .
The vibrations will load/unload the threads .
You'll be amazed how easy the nut turns .
No need for brute force , 3ft bars or broken fins ..
 
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dynodave said:
.. I also had one set of aluminum nuts, which I would only use as for a static display or for"show" and still antiseize them.
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I use aluminium nuts on my N15 , but with bronze threaded inserts in the head .
Not sure how long they will last , but they have been doing just fine for the last 150 000 km .
 
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Norman White recommended a smear of graphogen on the threads and the use of lock tabs when he re did the threads on my Atlas.
 
ludwig said:
I use aluminium nuts on my N15 , but with bronze threaded inserts in the head .
Not sure how long they will last , but they have been doing just fine for the last 150 000 km .
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There is no problem at all using aluminum nuts in a bronze insert. They last just fine.
 
comnoz said:
There is no problem at all using aluminum nuts in a bronze insert. They last just fine.
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I would agree, however I only put welded aluminum inserts...So no aluminum roses for me. The inserts I always put in were welded by by a excellent welder and the inserts after welding any minor warpage or splatter was chased away with the GH4 class tap. Stock roses always fit and seemed a tighter cleaner fit than in a stock heads.

When I started into nortons for the second time in the late 80's I pit crewed for Pete Kogut and started to use his "NE" spring tightening method.
shown here on my combat with armours stainless exhaust: http://atlanticgreen.com/images/exhsprrh.jpg
yes a bit uncosmetic for the "girly" esthetics but you could screw on a rose by hand only, clip on the spring, and it would continue to self tighten and you would never strip a head or loosen a nut.
 
Jeepers Dave, based on my experience every single fastener on a Commando could use that treatment!
 
I tried the spring tightening thing. It didn't seem to work for me. It should have worked but didn't have enough pull to actually tighten the nut even though there seemed to be plenty of tension on the spring (took a vice grip on the spring and a good hard pull to install). I caught it getting loose when I heard it rattle - it turned with a wrench and so I abandoned the spring tightening technique.
 
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ludwig said:
I said it before , but these exhaust nuts should be tightened with running engine .
Rev it to 4000 rpm and apply a constant pressure on the wrench .
The vibrations will load/unload the threads .
You'll be amazed how easy the nut turns .
No need for brute force , 3ft bars or broken fins ..
Click to expand...
That is brilliant!
 
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