Exhaust nut RTV / lock tight ?

Has anyone used the high temp RTV stuff made by Permatex called " Ultra Copper " on thier exhaust nuts? A friend who is a pro bike restorer of old American bikes suggested it to me. The reason is that it stays somewhat rubber like and would not allow the nuts to loosen up do to vibration. I am a little skeptical of it for a few reasons. #1 it would be hard to clean off after removing them. ( maybe years later) #2. I would need to be very careful not to allow any of it to squish out & possibly get on a valve stem. # 3. It may not work & in the back of my little mind running down the road I would be thinking I should have safety wired them too witch makes the stuff moot because the only reason to use it would be so I didn't need to drill holes in the nuts & safety wire them. My friend uses it on part of the exhaust system of a old style bike that has a tube press fit into another tube & he says it works and dose not allow the two parts to vibrate apart as they had for years before. Sounds good, just a little scary. I'm inclined to just use high temp anti-sieze & safety wire. What do you learned Nortonites think ???

I believe it is more important to lube the threads with anti sieze to attain the full effect of the thread against the squash washers. A snug up or 2 after heating will set the exaust nuts.
Resistance and gauling in the threads is what allows the nut to come loose after time and causes damage to the soft threads in the head.
As with plumbing, pipe dope is not a sealant but a lubricant. It is the positive contact of the threads that make the seal. I realize that we are speaking of straight threads, but the concept is the same.

I have been using RTV copper silicone on the exhaust for many years and have never had an exhaust nut back off on Crazy. Never ever , and I don't use stock retaining rings or safety wire (a sensible requirement for racing) . These items help keep an ever so slightly backed off nut in a potential zone of chattering at the delicate threads without the driver noticing over engine-exhaust noise. Smear it lightly on the clean threads and feel the smoothness threading in the ex.nut (always minding cross threading) , go for a drive after initial tightening then re - tighten in hot motor with a proper ex.nut wrench tool or BMW airhead tool - even better. I also use a slight smear of it on both sides of a properly annealed and quenched copper head gasket ,taking care to go real thin at the oil drain hole area as it could potentially stop it up. Permatex Ultra Copper high temp N0 101BR in a tube ,80 ml. May irritate eyes and skin ,do not breath fumes,keep out of reach of rug rats. Contains polydimethylsiloxane.

I would submit that Permatex Ultra Copper high temp N0 101BR acts as a threading lurbricant in this application and would agree that its effectiveness to bring the exhaust nut home to the squash washer could be as good as anti-seize. As far as a retaining compound, no.

I have found a little RTV works pretty well to keep the nuts from coming loose. Do not use locktite . Jim

And racing or not, I am a huge fan of safety wiring.

I don't know what the heat rating is, but would think the exhaust is hot enough to make loctite fail or loose it's locking qualities.

Thanks guys, you have quelled my fear that it be a bad thing. Still I think I will use it spairingly so as to not risk getting any of it on the valve. Can you tell me, how hard is it to clean off when you do take them apart again.????

just use a fine hand pick followed by a fine brass brush. Use less if worried. Protect those thread$

I never had an issue with loose exhaust nuts. But now I have the brass ones which I understand are even better. I always warmed up the bike after installing them and took a 3' extension on the nut wrench and gave them a nice tug while someone was holding the exhaust up. Seemed to work for me. No racing.

Dave
69S

The metal ones work fine w/o anything on them as long as you tighten them a few times after running the bike.

Why not just lockwire them ?

To tell the truth the use of the RTV was brought up by my friend when I was at his shop to use his drill press to drill the holes in my new Stainless nuts for safety wire. He ask me why I didn't just use the RTV witch in his mind would stop them from vibrating loose in the first place. I think as someone said here that even safety wire needs to be checked once in a while so that they haven't come loose that little bit & are vibrating around damaging the threads. The RTV would in theory, prevent that from happening. I think I will do both. To much of a good thing has allways been my rule of thumb.

plj850 , because lock wired ex.nuts look real ugly in my book ,also when your ex. nut does decide to back off it would be best to know about it via sudden ex. volume in ears. Then pull over and retighten to put in RTV copper first reasonable opportunity...on a long trip I would not want the delicate threads chattering to dust imperceptably because of a lock wire or worse, a stock 850 retaining ring . I have seen this happen to a friend on a long rally ride where we had to pull over and wrap found fence wire around the nut and then around the barells just to get on the road again. What a mess and the retaining ring self destructed , possibly from all the heat and vibration ,the retaining ring tabs being weakened fundamentally by bending over of the tabs as another potential factor. Thead replacement is expensive and a lot of labour to pull- refit head and not to mention downtime from mission no. one , riding.

I've use Ultra Copper for Al V8 boat wet manifold sealing, Worked a few hours of hard use then begins to blow out. I found it best to apply the goop then place parts but not fully tight and wait over night for RTV to set up. BTW about best highest temp anti-seize is Milk of Magnesia.

Oh yeah forgot that some cleaver souls affix a spring or springs to keep some
torque on the ring bolts. Nut have their treads inside of hole don't ya know.

Torontonian said:

plj850 , because lock wired ex.nuts look real ugly in my book ,also when your ex. nut does decide to back off it would be best to know about it via sudden ex. volume in ears. Then pull over and retighten to put in RTV copper first reasonable opportunity...on a long trip I would not want the delicate threads chattering to dust imperceptably because of a lock wire or worse, a stock 850 retaining ring . I have seen this happen to a friend on a long rally ride where we had to pull over and wrap found fence wire around the nut and then around the barells just to get on the road again. What a mess and the retaining ring self destructed , possibly from all the heat and vibration ,the retaining ring tabs being weakened fundamentally by bending over of the tabs as another potential factor. Thead replacement is expensive and a lot of labour to pull- refit head and not to mention downtime from mission no. one , riding.

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Each to his own I guess not sure why you think the exhaust nut would back off when correctly lock wired