Need Main Seal Advice

Hi all,

I installed a new main seal on the end of the crankshaft between primary and left crankcase last fall and despite being very careful in installation it continues to leak some engine oil into my beloved dry belt primary.

I am about to contact Norvil to order a new front belt sprocket and belt and would like to include with the order a new main seal.

If memory is correct the seal I have in place now has a thin metal circle piece surrounded by the rubber seal.

Am I correct that there is better sealing choice, an all rubber seal perhaps?

Is there a consensus of the "best" seal to order nowadays so that I am exact in my ordering with Norvil?

And is lock tite or something eles still advised to keep the seal from spinning in place?

thanks for any ideas

John

Place a piece of tape (I use Nitto electrical insulation tape) along the keyway to protect the seal lip. Pull the tape out gently when the seal is fully seated (Nitto doesn't tear like some others may).
Rubber shrouded main seals should not need additional sealant but the metal to metal type always does (e.g. one of the Loctite products maybe - not the cyanoacrylates though ).
Ta.

I've never had good luck with the metal shrouded seal, on several occasions even with sealant they eventually leaked again. I have not had this problem with the rubberised one and I am now on my 8th Norton rebuild.

A reed valve breather modification stopped all my leaks. After I did it, no leaking.... I bought 2 extra reed valves for my parts collection because I considered the modification essential to the design, even though it was omitted originally.... You get rid of the pressure, you get rid of the force causing the leak. Depending on what year bike you have, you could buy jim's sump plug breather and have a bolt on solution....

If you've spent so much on dry belt drive then I don't comprehend the lack of a cheap reed breather valve to prevent leakages. The seal should be replaced every time the primary is apart as a matter of course and it should be the outer rubberized type.

I have always used the metal cased seal installed with a bit of epoxy around the od and never had any leakage problems. I replace them at an average of 30,000 miles.

Some have better luck with the rubber coated seal. They do seal to a slightly different area on the crank so that may be the difference.

I always found the rubber coated seal got hard sooner. Jim

I had the leaking main seal problem recently. Tried several seals, metal edge, used Jim's epoxy method and no joy. Went to the rubber encased seal
and that ended the leak. With a belt you cannot have a leak. With the standard setup I doubt you would know it leaked or not unless you had a gusher.

More frequent seal replacement wont bother me it is easy and cheap. Do mind the advise of using tape protection on the threads esp the part
that the tape withstands removal. Weak tape can break apart.

Perhaps the rubberized seal is the one you will find here.
Scroll down, just below his belt drive system.

http://www.stevemaney.com/products.html

Thanks for the replies!

And yes, I have had a reed breather installed for many
years now.

The only time I have replaced this seal is when rebuilding, I have always used the seal that came with the gasket set, I just put them in without any goo or sealant (tight fit), I have never had one leak in all the 40 years of ownership the ones that come in the gasket kit are the metal on the outer, the last motor I rebuilt for a mate was the all rubber one and I think I used a bit of sealant on the outer edge, when I slide the case over the crank I put a bit of grease on the seal so it don't get damaged, I also do this when I put the timming cover on (points seal) without the speical tool, have never damaged a seal by doing this.

Ashley