Sealing Base & New Studs

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Anonymous

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I am replacing the studs that bolt the 1971 Barrells to the cases. The nuts were cycle 26 tpi & difficult to get local. I am replacing them with the unf 24 tpi later type. My questions are: Would you use a thread sealant b4 screwing them into the cases ? Also, I read in an earlier workshop manual to not use the cylinder base gasket as they were prone to break and then you had oil leaking. It advises just using a gasket sealant. Has anyone got any advice ?
Thanks in anticipation.
nortonfan
 

Ron L

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Are you making 24 tpi studs? If so, are you planning to use heli-coils in the aluminum cases? I believe the end of the stud screwing into the aluminum is something like 22 TPI. You don't want to use fine thread in the aluminum. The original 26 tpi nuts are not that difficult to find and are even available in stainless. I'm not sure why you want to go to this much trouble.

Using thread sealant would not be necessary if the threads are a good fit. If not, then sealant might help but I would be concerned about the strength.

As far as joint sealant for barrel to case, I use Loc-tite master gasket, an anaerobic sealant. Do NOT use silicone. There are a number of other brands, but make sure it is anaerobic. These do not cure in the presence of air. This prevents any balls of cured sealant from being lodged in the oil passages.

Ron L
 
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I agree with Ron on this your messing with one of the weakest areas on a 71 engine case. If you have the motor still down you may want to use some spray can crack test made for alum. around the drive side crank shaft boss 71's were weak there. Several years ago I got a set of 73 replacment cases from Domni Racer in Ohio for around 200.00. these are renfoced with webing but require the oil pick up mod be done to them. The crack test kit is made by Sherwin and has three cans, cleaner DR-60, Penetrant DP-51 and Developer D-100 Mc Master Carr might be a source for the kit. norbsa
 
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If you are going to just ride the bike mildly. You may want to look into making a metal base gasket . Stock base gaskets crush down to .010 of an inch so if your good at sheet metel fab you can trace a base gasket on to a piece of Sheet metal .050 thick this will drop your compression ratio down one from 9-1 to 8-1 this takes away some vibes and makes it easyer to run pump gas.The loss of performace is not very noticable. If your plan is to leave the bottom end unrebuilt this might make it last a little longer. Mc Master Carr would be a good source for sheet metal this thickness look for shimm stock in the catolog.norbsa
 
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Thanks

Thank you for your replies. I wanted to replace the old studs & am just using the 1972 & on original Norton replacement part. The thread into the cases is coarser at 16 tpi & I am not touching them at ball. The threads in the cases seem nice and firm, but I wanted to get opinions on a sealant, just in cases it helped. I have purchased a recoil kit for the 3 head studs that go thru the barrells as 2 of em were buggered.

It appears Ron L does not use a gasket at all then ??

I have been waiting 6 months for the replacement parts from my supplier here in Oz & thought I may as well just put the later ones in.

Thank you again for your input/suggestions.
nortonfan
 
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Just a drop of Loctite 518 Gasket eliminator on each stud should stop any weaping and can also work for a base gasket. norbsa
 
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Thank you all for your input/advice.

As you probably all know, the earlier commando barrel nuts were 26 tpi cycle thread, then from 1972 on they decided to use 24 tpi UNF.

As the threads are that close to look at...it would be easy for a person to try putting the wrong nut on..well someone like me anyways :)

Anyways, the tansplant has been a success :D

I haven't used a norton barrel gasket, so I will let you know what happens.

Also fitted my disc brake wheel back on after having the rim rolled, chromed and new stainless steel spokes fitted. A brembo master cylinder tops it off from CNW and doesn't that feel good :D

Aren't nortons' "A work of Art", it is so easy to sit back with a beer and admire their looks. They must be female.

Reg.
 
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