any tips for a leak free installation of the primary case O-ring seal?

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joe czech

joe czech

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not a significant leak - kind of minor, no drips, just a little seepage. usually don't have O-ring issues - installed a few over the years but this primary case O-ring is a bit of a booger. installed new TWICE, and still getting a little seepage. fairly sure the O-ring groove is okay - same for the outer case flange surface - appears to be flat - no other issues. installed the O-ring with a light coating of general purpose, synthetic blend, grease. hold down bolt torqued to spec. so, any installation suggestions, or is a little seepage somewhat normal?
 
I have always used a light smear of clear RTV around the outer cover face. Wait for it to cure overnight before adding oil.
 
Before you install the oring, bolt on the outer cover and using a feeler gauge check that the gap is equal all the way around. If it isn't you need to rectify the problem or it will never stop leaking. Are you sure the leak is from the outer cover seal and not the alt. wire bushing or the mainshaft seal?
 
I finally solved mine from leaking.I use the o ring then I used to put silicone from halfway up the front,along the bottom and halfway up the rear.Then leave the plug out 24 hrs and then fill. It worked for awhile then weeped again. I thought there was a possibility there was a small amount of crankcase pressure.I drilled and tapped just halfway up the inner primary one winter just ahead of the clutch basket and inserted a 90 degree small pipe fitting with a 1/4" barb on it facing 45 deg to the rear.Then I put a 1/4" hose venting to the battery box.Sort of like a battery vent.Don't ask me why but it seems to work.It is something to consider when you have the primary apart in the winter when you have some time.Hope it works for you but I have done it on 2 of my commandos and it seems to work.
 
milfordite said:
Before you install the oring, bolt on the outer cover and using a feeler gauge check that the gap is equal all the way around. If it isn't you need to rectify the problem or it will never stop leaking. Are you sure the leak is from the outer cover seal and not the alt. wire bushing or the mainshaft seal?
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thanks for the tip - will check the gap w/o the O-ring. everything on the inner side of the inboard primary case is dry, so i'm assuming the main shaft seal, and alternator grommet seal are good. the seepage is definitely from the O-ring sealing surface.
 
bchessell2 said:
…thought there was a possibility there was a small amount of crankcase pressure.I drilled and tapped just halfway up the inner primary...
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believe it or not, I actually thought of something similar. I have several spare inspection caps - might drill a small hole in one (maybe the timing tab port) and see if that has any effect.

been working my butt off to get this thing bone dry - primary seepage is the last issue. overall, best I can tell, it's running great - smooth acceleration through the gears and throttle. have nothing to compare it to, but I have no complaints.
 
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Not sure how pressure could build up in the primary case, as the inner only has a felt "seal" around the output shaft. No way that holds pressure.

I use hylomar blue on the o-ring and it seems to be very good. I had used Permatex Grey and that held too well, making a very hard cleanup next time I needed to R&R the cover.
 
Tornado said:
Not sure how pressure could build up in the primary case, as the inner only has a felt "seal" around the output shaft. No way that holds pressure.

I use hylomar blue on the o-ring and it seems to be very good. I had used Permatex Grey and that held too well, making a very hard cleanup next time I needed to R&R the cover.
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I agree on the pressure build-up within the case - just grabbin' at straws a little. I do have a tube of hylomar blue - may give it a try. thanks....
 
joe czech said:
not a significant leak - kind of minor, no drips, just a little seepage. usually don't have O-ring issues - installed a few over the years but this primary case O-ring is a bit of a booger. installed new TWICE, and still getting a little seepage. fairly sure the O-ring groove is okay - same for the outer case flange surface - appears to be flat - no other issues. installed the O-ring with a light coating of general purpose, synthetic blend, grease. hold down bolt torqued to spec. so, any installation suggestions, or is a little seepage somewhat normal?
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page 6 Joe
https://www.accessnorton.com/NortonCommando/why-we-call-it-inspection.24374/page-6

dry as a bone.
And, once you put the plug in, those inanimate objects aren’t repulsed by RTV squeezed into funny shapes.
 
Joe, do you have a breather reed valve ( homemade, NYC, Jim Comstock, Jim Schmidt) fitted ? if not any of these will help alleviate oil leaks, as they create a partial vacuum in the cases. the NYC/ Comstock will also clear wet sumped oil sharpish.

Cheers,

cliffa.
 
any tips for a leak free installation of the primary case O-ring seal?
 
just to repeat the first sentence on my original post - "not a significant leak - kind of minor, no drips, just a little seepage." it just may be I need a better O-ring or O-ring material. may start a little research in the aerospace industry. maybe a silicone based material vs current service replacement rubber. I know fel-pro has a blue silicone rubber valve cover gaskets for iron head small block's that solves a multitude of leaking issues - maybe something similar would apply here. thanks for all the suggestions so far - lots to think about.
 
When I first got my bike, I fitted a soft compound o-ring recommended by Walridge. Quite squishy, almost like a foam. Sealed fine. But it broke at the joint when I was R&R'ing the cover to address sticky clutch plates. Slapped a stock harder rubber ring with the Permatex....again no leak but it was a fair bit harder to fit the ring into the groove etc. And it also split at the joint the next time I had cover off. After a good hour of scraping the Grey sealant out the groove, I replaced with another stock rubber, Hylomar'd. ATF Type F in the casing and not a sign of leakage still. I've heard others use windshield washer type hose for this seal, using silicone to seal the ends (positioned at top of casing).

I don't think you need to over think this with higher tech solutions. If it ain't sealing to your satisfaction trying a different goop and confirm the sealing surfaces are proper level.
 
The inner primary must be shimmed on It's central support post to achieve perfect flatness first. The sealing band large outer rubber gasket is best seated with any imperfections like casting marks or splits best placed over the stator top position where less oil is likely to be thrown about. Once you are fed up with this action you will purchase a belt drive kit and run things dry. And lighter. And smoother. $$$.
 
Tornado said:
I don't think you need to over think this with higher tech solutions. If it ain't sealing to your satisfaction trying a different goop and confirm the sealing surfaces are proper level.
Click to expand...

"over think things" - another one of my bad habits - :D
 
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