stud replacement

fastback · Apr 11, 2007

Hi there,

I have lost the front center stud holding the barrel to the case. PO had installed a bolt, the bike spit it off in disgust it seems

Is there any reason I shouldn't just clean out the threads with some spray solvent and compressed air, then pop in a new stud with some Locktite and top it off with a nut? I'm hoping there isn't a nasty surprise lurking in the casing.

I don't want to pull the bike apart at the moment.

Thanks, Phil

Ron L · Apr 11, 2007

Do you mean the stud between the carburetors? It might be difficult to get a stud in there with the double nut technique due to tight space.

fastback · Apr 11, 2007

Hi Ron,
No, the other front! :wink: above the front iso.

I was concerned that I would be blowing dirt into the cases, but I guess I would have noticed a bit of breathing out of the hole if that was true.
Phil

79x100 · Apr 11, 2007

It probably depends on the individual casting whether the drilling has broken through or not. On the basis that it would be p*****g out if it could, it sounds as if you're in luck.

Your solution might hold for a while but will probably be less rigid than original so best to avoid track-days in my opinion :wink:

debby · Apr 11, 2007

Some of the cases had a blind drilling for that stud, others were drilled through. You must have one of the blind ones (easy to check) or you would have had a real oil geyser! That stud is right above the cam, lots of oil being slung around there.

Seems like it should be ok just to replace it if you have enough room to double-nut it or get a stud box in there.

Debby
72 750 Roadster
74 850 project

fastback · Apr 11, 2007

Thanks - that was my hunch but I just wanted to be sure!

Next thing to tackle - getting my carbs happy.

Ron L · Apr 12, 2007

Duh.. I read barrel to case, but was thinking head to barrel. I see no reason why you could not replace that stud in-situ, unless the stud is actually broken off in the hole. Whatever you do, do it soon. Running just one stud loose on a 750 will soon have all of them loose and then the barrel starts to lift and tilts in the cases and cracks them.

This is the main reason Norton started recommending the elimination of the base gasket and using anaerobic sealant. The switch to the thru-bolts on the 850 was the final fix. Check those cylinder base studs often on a new rebuild!

fastback · Apr 12, 2007

Thanks for the additional info Ron - good to know.

pommie john · Apr 12, 2007

ron L said "Running just one stud loose on a 750 will soon have all of them loose and then the barrel starts to lift and tilts in the cases and cracks them. "

I have always used a base gasket and I've had to tighten the base nuts after every race meeting. To find out if it was the gasket compressing or the nuts unwinding, I put some paint blobs on the nuts, and it turned out to be the nuts loosening off.
I have always been suspicious of running without a gasket. What kind of sealant is anaerobic?[/quote]

Keith1069 · Apr 13, 2007

Had the same problem on my Combat cases but you have to ask why there was a bolt in there! Did the case threads strip and someone put a different bolt in? Mine had an M10 bolt fitted when bought. The threads aren't that deep on a through hole so if you have a blind hole how much engagement really is there? Just a thought, but as the others say get it fixed sooner than later.

Ron L · Apr 13, 2007

Pommie John,

Anaerobic sealants are those that cure in the absence of air. Examples are Loctite Master Gasket 518 or Hylomar Gasket 2000. Norton sold these as Loctite Gasket Eliminator.

I use these as sealants for case halves and any area where circulating engine oil is present.

pommie john · Apr 13, 2007

Ron L
Thanks for that, I'll try one of those on the next rebuild.

Jason Curtiss · Apr 13, 2007

Hey fastback, it's good to hear from you again; it's certainly been a long time. I thought perhaps you had switched to another brand, like Guzzi.

Make sure you can get full thread engagement before you apply the Loctite. As Deb said, its a blind hole so you should be able to blast it clean with compressed air and get a good visual of the condition of the threads.

If the threads look good run the stud in by hand to check the fit and engagement. If all looks and feels good then apply your favorite thread-locker and run the stud in for real.

Jason

fastback · Apr 14, 2007

Thanks again.

Yes, it has been a busy winter, haven't touched my Norton all winter :cry:
Will start with fresh fork seals next week!

Phil

fastback · May 8, 2007

I've got my replacement stud and taken a look down the rabbit hole as it were - didn't like what I found - could be worse. It's stripped. Can you recommend a helicoil kit? Is there a reasonable source for kits.

The stud is 3/8 x 16 x 26 - the 16 being the case end - Is that UNC or cycle? I want to do it in situ with the barrels off, already have the head off at the moment.

I plan a full top & bottom rebuild next winter - I just want to be sure things don't self-destruct this season.

Phil

stud replacement

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