DAMN Crankshaft SEAL

1up3down · Mar 31, 2016

situation: 73 850 with mostly dry belt primary

problem: leaking engine oil past the seal and into the primary

1) gearbox oil level is slightly below the inspection bolt level so very doubtful oil coming in from there

2) in the last 8 months have installed three new seals, both kinds - all rubber and rubber and metal

been very careful lock tight securing the seal, slowly sliding it over the lubricated shaft and into place

a 20 mile ride yields a couple of shot glasses of oil when pulling the primary cover

anyone know any secrets?

swooshdave · Mar 31, 2016

Breather?

pete.v · Mar 31, 2016

Lower right primary to crankcase bolt hole?

Onder · Mar 31, 2016

Since I had a similar problem I have to ask:
Is the crank surface where the seal touches the crank compromised? Does the
crank move left and right when hot and reach bad areas or pass over them?
Have you dialed the crank just to be certain it isnt bent?
When you put the seal in, did you put cello tape over the threads?
Have you let it sit and then with a strong glass see where the oil is passing
whether outer or inner?

Im just asking. I put on a Comnoz sump valve and it has reduced the oil
in the primary to a teaspoon every 500 miles. However I still have a leak
at the bottom of the cases. Tried sealing the threads and body of the
valve but no joy.

These things are sent to try us.

davamb · Mar 31, 2016

Same problem and I'd like to know the answer too. Replaced main seals (twice) and fitted annealed copper washers for the three mounting screws. Haven't checked crank float though.

1up3down · Apr 1, 2016

yes, breather installed

yes, inner primary mounting bolts nice and tight

I give up, resigned to taking off the outer cover, draining and wiping out oil too damn often.....

gtsun · Apr 1, 2016

Never had this problem but I think it's a good idea, or a necessary one typo "seal" the threads of the inner primary mounting bolts to keep oil from passing down them. Also smell it, it could be gear oil coming down the shaft. Get one of the bolts with the seals from... Aaa can't think of his name right now but many here do. Do a search for it, it'll come up. I don't think just keeping the gear oil level below the inspection hole would keep it from going down the shaft.

Onder · Apr 2, 2016

A blessing of rear sets is you get one nut removal of primary cover with nothing in the way. Takes
a few minutes to remove, wipe and replace.

Beach · Apr 2, 2016

The guy that does that seal for mainshaft goes by DynoDave....I highly recommend it...

o0norton0o · Apr 2, 2016

I'm not one of the forum experts, but common sense tells me to look at 3 things...

main bearing play- no seal will last if the bearing doesn't run true

crankcase pressure- If your breather set up works poorly, you get more pressure at all your seals and gaskets. I think most of us have solved various leaks by relieving crankcase pressure rather than some mystery part that seals better.

shaft pitting- If your crankshaft is pitted or rough right at the seal area, perhaps it's wearing out your seal quickly or has a nick that is allowing oil to pass the seal. Maybe give a look with a magnifying glass to see that all is well there...

nortriubuell · Apr 2, 2016

1up3down said:
yes, breather installed

yes, inner primary mounting bolts nice and tight

I give up, resigned to taking off the outer cover, draining and wiping out oil too damn often.....

Well, don't "give up" :evil: There IS a reason, ya just haven't found it ... yet. That's what the forum is for, cheers.

comnoz · Apr 2, 2016

How is your oil tank vented? Jim

jseng1 · Apr 3, 2016

The easy way to find an oil leak - get some "bubbles" from a toy store. Drain the sump. Connect an air hose to the engine breather (bypass the Comstock one way valve). Plug up any vents. Apply about 15 psi to the crank case. Paint on the bubble liquid with a brush and you will see exactly where the leak is.

I got this tip from the propane people who use the bubbles to detect leaks. The other option is to immerse the motor in a tub of water before applying air pressure and I've done this to find cracks in the cases of racing motors.

DAMN Crankshaft SEAL

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