drive side crank seal leak 74-850

Onder · Aug 21, 2014

I have a leak on the drive side seal. 500 miles! Read the threads and got the little tool, quite handy. Seal shows no wear or damage and was squarely driven home. Since I run a belt, the oil was spotted early on. Im puzzled as I also have the Comstock crankcase valve which I would think would lower the case pressure a good deal precluding any leaks.
Since the leak appears to be more around the ouboard edge of the seal to the case, a sealant might do the deed. Problem is, what is the recommended sealant?
Think I saw Jim using J B Weld which is fine but for the worry of never being able to get it out without a complete teardown.
Recommendations?

Torontonian · Aug 21, 2014

Permatex Motoseal 1. Grey gasket Maker. Pricey but I love it. I'm sure others will recommend other goopy products. The seal with rubber that goes all the way around the outside seems to work best re: this outer seal leakage topic. As for the inner to crank-end life, it seems to be about 10 years, but others will quickly testify theirs lasted much longer. Hobot's method of putting machine screws into it to remove by tugging worked well for me. Good Lucky.

mike996 · Aug 21, 2014

Torontonian said:
Permatex Motoseal 1. Grey gasket Maker. Pricey but I love it. I'm sure others will recommend other goopy products. The seal with rubber that goes all the way around the outside seems to work best re: this outer seal leakage topic. As for the inner to crank-end life, it seems to be about 10 years, but others will quickly testify theirs lasted much longer. Hobot's method of putting machine screws into it to remove by tugging worked well for me. Good Lucky.

+1 Permatex motoseal is the only engine-related sealant I use on: motorcycles, cars, boats.

Onder · Aug 21, 2014

Source on rubber edged seal?

comnoz · Aug 21, 2014

Onder said:
I have a leak on the drive side seal. 500 miles! Read the threads and got the little tool, quite handy. Seal shows no wear or damage and was squarely driven home. Since I run a belt, the oil was spotted early on. Im puzzled as I also have the Comstock crankcase valve which I would think would lower the case pressure a good deal precluding any leaks.
Since the leak appears to be more around the ouboard edge of the seal to the case, a sealant might do the deed. Problem is, what is the recommended sealant?
Think I saw Jim using J B Weld which is fine but for the worry of never being able to get it out without a complete teardown.
Recommendations?

I would use JB weld. It does not make the seal hard to remove in the future. It is the only thing I have found that you can count on to keep the seal from leaking around the outside when the case gets hot and expands away from the seal. Jim

I have watched seals that seemed to be a nice snug fit when installed, actually turning with the crank a few hundred miles later when the engine is hot.

worntorn · Aug 21, 2014

+2 on the Motoseal as a good product.
Though not in the same application as the OP, I used it to seal my cylinder base joints in place of a couple of leaky paper type cylinder base gaskets. Just lifted the cylinder enough that the rings were still in the bores so as to keep the ring seating. I then pulled out and threw away the old paper gasket, washed the two mating surfaces with acetone in a very hit and miss way, then applied the Motoseal and dropped the cylinder back down. That fix has held for ten + years now and many thousands of miles.

Glen

comnoz · Aug 21, 2014

worntorn said:
+2 on the Motoseal as a good product.
Though not in the same application as the OP, I used it to seal my cylinder base joints in place of a couple of leaky paper type cylinder base gaskets. Just lifted the cylinder enough that the rings were still in the bores so as to keep the ring seating. I then pulled out and threw away the old paper gasket, washed the two mating surfaces with acetone in a very hit and miss way, then applied the Motoseal and dropped the cylinder back down. That fix has held for ten + years now and many thousands of miles.

Glen

Motoseal is a good product but I have found it will not hold a mainseal in place.

I have not had very long life when trying to use the rubber od seals. They usually ended up leaking through a worn lip at the crank much sooner than the metal seals although they do seal in the bore better. Jim

Onder · Aug 21, 2014

Thx Jim, I totally ignored the head expansion issue but it sure makes sense. After all we heat alloy to pull out bearing etc. Ill use the JB despite the fact that the
"high torque" permatex is really tenacious stuff.

1up3down · Aug 21, 2014

oh damn!

I am in the process of installing my new Alton Estart today

and because I had a small amount of oil in my dry belt primary I put in a new main seal today

and did not remember to put any kind of stuff on it to keep it in place

it did go in nice and tight

so I suppose it is going to spin on me and leak oil again? can't dig it out now

Did the factory put some kind of sealant around it way back in the 60s and 70s?

comnoz · Aug 21, 2014

1up3down said:
oh damn!

Did the factory put some kind of sealant around it way back in the 60s and 70s?

Hard to say, probably a little shellac.
Did they leak in the 60s and 70s? Yes

There are probably other things besides JB weld that will hold the seal in place -at least most of the time. I use JB weld because it holds first time every time. I tried a lot of different things before I decided to try JB weld. Jim

dero · Aug 22, 2014

Could somebody please direct me to hobots method of seal removal .

olChris · Aug 22, 2014

dero said:
Could somebody please direct me to hobots method of seal removal .

Joking , Just PM him he's cool....

tomspro · Aug 22, 2014

comnoz said:
I would use JB weld. It does not make the seal hard to remove in the future. It is the only thing I have found that you can count on to keep the seal from leaking around the outside when the case gets hot and expands away from the seal. Jim

I have watched seals that seemed to be a nice snug fit when installed, actually turning with the crank a few hundred miles later when the engine is hot.

Just to be clear, are you recommending applying the JB on the rim of the seal before insertion, or on the outside after it is in?

Onder · Aug 22, 2014

Im not answering for Jim but in construction, NOTHING seals from by application on the outside when the problem is coming from the inside.
Doing the job in a few minutes and the bore will be cleaned with MEK, the rim of the steel edged seal likewise and then drifted in. Minimal
amount of JB poop will be used in the bore before seal goes in.
I must repeat that the little Lisle 58430 seal puller makes it all easy.

tomspro · Aug 22, 2014

Thanks for that reply Onder.
Seems like a seal puller of some kind will be REQUIRED after applying the JB weld the next time removal is called for.

comnoz · Aug 22, 2014

I use a light film of JB weld inside the bore before I push the seal in place. Do not use so much that it would be pushed into the bearing when you push the seal in. I use a pocket screwdriver to apply a thin coat.
Make sure the OD of the seal is clean and dry before you push it in. A light film of oil on the inside of the seal is a good idea. Put a piece of scotch tape over the keyway slot before you push the seal over the shaft. The tape can be pulled out after the seal is installed.

Wipe any excess JB weld from outside of the seal before it dries. JB weld that has set up around the outside edge of the seal could make the seal hard to remove next time.

When you need to replace the seal I use a sharp awl and punch a hole in the seal and screw a small metal screw into the seal to pull it out. You will see a little bit of JB weld that was behind the seal after the seal is pulled. There is no need to remove it. Just re-apply a thin coat of JB weld and push the new seal in. Jim

Torontonian · Aug 22, 2014

B.T.W. this happenstance lucky seal retention from the factory was all changed in 1975 when they must have heard about drifting-leakage problems . A circlip is used to hold it firmly in place. Today's super-duper glues sure beat whatever they used then. Still can't fathom felt seal for primary mainshaft. :|

comnoz · Aug 22, 2014

Torontonian said:
B.T.W. this happenstance lucky seal retention from the factory was all changed in 1975 when they must have heard about drifting-leakage problems . A circlip is used to hold it firmly in place. Today's super-duper glues sure beat whatever they used then. Still can't fathom felt seal for primary mainshaft. :|

Even with the circlip -which only keeps the seal from being pushed out by crankcase pressure - you still need to keep the seal from turning or leaking around the OD. My bike is a MK3 with the circlip and I fought with it for years before I learned. jim

tomspro · Aug 22, 2014

comnoz said:
I use a light film of JB weld inside the bore before I push the seal in place. Do not use so much that it would be pushed into the bearing when you push the seal in. I use a pocket screwdriver to apply a thin coat.
Make sure the OD of the seal is clean and dry before you push it in. A light film of oil on the inside of the seal is a good idea. Put a piece of scotch tape over the keyway slot before you push the seal over the shaft. The tape can be pulled out after the seal is installed.

Wipe any excess JB weld from outside of the seal before it dries. JB weld that has set up around the outside edge of the seal could make the seal hard to remove next time.

When you need to replace the seal I use a sharp awl and punch a hole in the seal and screw a small metal screw into the seal to pull it out. You will see a little bit of JB weld that was behind the seal after the seal is pulled. There is no need to remove it. Just re-apply a thin coat of JB weld and push the new seal in. Jim

THANKS JIM!
Sounds like a good procedure to minimize oil leaks into the primary.

drive side crank seal leak 74-850

Similar threads