Transmission Mainshaft Seal

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Transmission Mainshaft Seal


Post by Ripley/Fla » Tue Mar 11, 2008 10:55 pm

Sorry, but I have to ask. My bike was basically unrunning when I bought it. I did some minor work on the gearbox, filled it with oil and let it sit. The main seal is leaking. Removed the trans sprocket and seal. The spring on the seal faced outward toward the sprocket. I believe this is wrong? To me, the garter spring side on a seal is the 'pressure side'; it is the side that faces in. For want of a better description the spring side ( if there is one) keeps what's inside, inside. I drilled three small holes as per the manual and used long deck screws with a puller to remove it - so I did not get it turned around after removal. I have ordered a double lip seal for its replacement. Thanks for any input.

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Post by steve_wood » Tue Mar 11, 2008 11:07 pm

I believe you are correct. I'm doing the same procedure myself. The double lip seal is a bit of a puzzle though. The one from James doesn't have a visible garter spring so it takes a bit of looking to figure out which side goes in....


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Post by jellero » Wed Mar 12, 2008 2:08 am

double up on the clutch rod seal too. i bought a tranny filler plug at the auto parts store, drilled and tapped it to accept a schrader valve, then shot in about 5 lb. psi air and sprayed with soapy water and it was a bubble machine (after sealing breather). this was after installing new james gaskets. so sealed everything up and almost zero seepage. j

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Post by Panacea » Wed Mar 12, 2008 4:03 am

The outside of the seal is all metal, the inside is where the spring is located. If your mainshaft bearing is excessively worn the new seal will fail quickly, grab the end of the shaft and try to wiggle it up and down to check for play, running your chain too tight can be the cause. there should be no "shake" at the end of the shaft.

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Post by fourthgear » Wed Mar 12, 2008 5:11 pm

You might not be able to use the cork seal that is between the trans case and the mechanical seal , some double lipped seals are thicker and don't forget they have to be recessed a little ( off the top of my head I can't remember how much exactly , but its a couple of thou.)
As said if there is worn bushings or bearings it will leak again in short order. Another thing I do is make sure the trans case where the seal is pressed in is not deformed or has nicks or large deep scratches and I use Acetone to clean the case and use a little RTV sealant to make sure it does not leak from the case to seal fit . Some of the new seals are coated with some kind of rubber or some thing to help in that area.

I do not hammer my seals in any more , its a good way to distort a good seal .They make good tools to seat them now a days .

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