Oil leaks

Paul1972 · Mar 25, 2010

Any sugestions on the best way to seal a primary chain case? Someone told me silicon was a good option?

Also the oil tank return pipe is leaking where it joins the top of the tank even with two union clips on. I don't want to over tighten the clips, what size should the rubber pipe be?

Any help to the above questions is much appreciated

pete.v · Mar 25, 2010

Have you had your primary off lately?
I believe the best and only way to seal the primary is to verify that the surfaces (inner and outer) match up proper. Behind the inner at the mounting stud in the center is were shims go to bring it all home (square). " 060399 3/8" Washer Shim, .027" Thick" Otherwise, when securing the outer at the center bolt you will flex at the point were the inner mounts to the crankcase causing warpage at the mating surfaces and therefore areas that will not seal even with a new o-ring . This needs to be done, of course, before final assembly. There will alway be an issue unless done right. I hope this is not too bad news.

Paul1972 · Mar 25, 2010

Nice one, I will give it a go. Thanks

Baldrick · Mar 25, 2010

Check RGM motors they have a special square section primary chaincase O ring?

Having said that I put it on and 5 minutes later I put a belt drive on and it cured any oil leaks...he he!

Danno · Mar 25, 2010

Before I swapped the '71 750 motor for the '75 850 (with the new style primary case) I used to run a bead of silicone in the groove of the inner half and push the o-ring into it. Then, before it dried, I'd use the outer to press the o-ring into the silicone uniformly, then take the outer back off and let the silicone set up before buttoning it up. I used a similar method with the new-style case's gasket, only with Hylomar or Yamabond between the gasket and the inner half.

maylar · Mar 25, 2010

I always run a light smear of RTV on the outer cover edge where it butts the o-ring. Never had much trouble with the o-ring in the groove. The only primary leaks I get are around the chromed centre securing nut, but that's just a dribble.

The rubber hoses are 8.7 mm I believe, about 3/8 inch. Look carefully as the leak may be comming from a crack in the tank around where the rear mounting tab is welded to it.

rvich · Mar 25, 2010

Danno,
I would say that is a pretty good idea, as in theory if the faces are not mating properly the silicone would fill the void behind the O-ring when you use the outer cover to push it into place. I would just add that you don't want to over tighten the outer case on the first fit-up so that you don't squeeze out all of your goo.

Russ

swooshdave · Mar 25, 2010

rvich said:
Danno,
I would say that is a pretty good idea, as in theory if the faces are not mating properly the silicone would fill the void behind the O-ring when you use the outer cover to push it into place. I would just add that you don't want to over tighten the outer case on the first fit-up so that you don't squeeze out all of your goo.

Russ

I think, if like he said, you let it set up a bit it might not squeeze out.

ILLF8ED · Mar 25, 2010

The biggest leak from my primary case comes from the felt seal around the gearbox out manshaft. How that's supposed to seal eludes me especially if using ATF...too thin. The oil runs down the inner case and drips from the bottom - looks like the rubber seal isn't working.

Danno · Mar 25, 2010

rvich said:
Danno,
I would say that is a pretty good idea, as in theory if the faces are not mating properly the silicone would fill the void behind the O-ring when you use the outer cover to push it into place. I would just add that you don't want to over tighten the outer case on the first fit-up so that you don't squeeze out all of your goo.

Russ

Yeah, I would just sort of hold it together by hand for a second so the silicone would hold the o ring a uniform distance from the outer half.

ML · Mar 28, 2010

illf8ed said:
by illf8ed » Thu Mar 25, 2010 4:03 pm
The biggest leak from my primary case comes

Yep, the factory knew this too, just before they released the Mk3, they brought out this inner case collar version for the Mk2's. Fits all pre-electric Commandos and stops the leak down the back from that poxy felt seal.

Mick

regental · Mar 29, 2010

Out of interest, is the above collar piece still available? If so, any idea of the part number? Thanks Alan

pete.v · Mar 29, 2010

I'm not saying they're not available but I could not find it like the one you see. I replace my the plates during a beltdrive conversion and I took one of these off. I could have saved it but cause I am dry now I do not need it.

DogT · Mar 29, 2010

I have heard of this inner primary case collar, but have never seen one. Cool. If anyone can get a part number or source. I am sure we would all appreciate it. I know I had mucho oil come out of that dumb felt seal, and it gets on the chain and then is all over the bike and it appears as if the primary chaincase is leaking because the oil drips down to the lowest part, the primary chaincase.

Dave
69S

grandpaul · Mar 29, 2010

That late style mainshaft seal gizmo must have the two halves tack welded together to effect the installation.

... just so's you knows...

ML · Mar 29, 2010

regental said:
Out of interest, is the above collar piece still available? If so, any idea of the part number? Thanks Alan

Sorry guys, another oddity from Norton, there is NO part number! Check with US Commando dealers, most know of this item. Its a job that reaquires removing the inner primary case, drill out the spot welds on the leaky flat lates, fit the new collar plate with a mandrel to centralise them, and either re-spot weld or drill 4 holes and pop rivet them. Also before putting the new collar plates togther, fit that damn felt seal in the recess. But it works....no silicon on the rubber band ever.

Mick

Oil leaks

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