My Oil leak list

The shake out of the project bike has produced three oil leaks.
-The Tachometer drive. I was hoping a new "O" ring would work for awhile. I guess I'll send it off to be milled for the Honda(?) rubber seal.
- The Primary case . Not sure what can be done here if the shims behind the inner case are already correct. Or are they?
- The kick start is the worst of the three. I'm going to replace the oil seal with another new one, assuming I damaged the original during assembly. Unless there is more to this problem than I might be aware of?

Advice on how you fixed these leaks on your bike would be helpful.

PS: don't suggest I fix my primary by installing a belt drive

Primary cover warped? Lay it on a flat surface and see what you get.

I believe its a Yamaha V-ring seal that goes in the tach drive, but its an easy, cheap fix.

With the primary, make sure the center of the outer cover hasn't been pulled in over the years. You should be able to turn the nut at least one full turn after the o-ring makes full contact to the inner case. If it is deformed, careful work with a rubber mallet should return it to its original shape. I assume you checked both halves on a flat surface before assembly.
- also, make sure the joint on the o-ring is on the top half of the cover.
- I paint my o-ring with Permatex Aviation Form-a-gasket (the greenish-brown stuff) or High Tack Gasket Sealant (the red stuff) before assembly - not effected by oil, and cleans up easily with acetone.

You may have nicked the o-ring on the kickstart shaft. Once replaced, try assembling with a bit of grease on the o-ring to ease it over the shaft.
- also, make sure you haven't overfilled the transmission. If you didn't measure the gear oil, stand the bike upright on level ground or on its center stand. Open up the plug on the back of the cover - only a drop or two should dribble out. Overfilling just encourages leakage.

Three is good - I think I had about ten leaks when I first started my Commando back in '08

One thing that can help the engine leaks is a good breather.

For the kick start seal there are a number of approaches including installing a lip seal. There are a number of threads on this site that touch on it.
I found I could get the standard seal to work very well by using a trick.
I'll assume the bush behind it is not worn, since if so the shaft would move too much, making a seal difficult.
When installing the new seal I intentionally over drove the bush in, causing the seal to bulge out more than normal into the space the shaft goes through.
This caused the seal to press more tightly against the shaft. So tight that the kick arm even returns more slowly than before. No leak after 800 miles.

I assume you know to remove old seal requires heating cover and banging it on a wood block to pop out bush.
To install again chill bush in bag of ice cubes, heat cover, drop in seal and drive in bush.
I found a cheap electric paint stripper gun works fine and maybe less hazardous and intense than a torch.

As to the tac drive leak do you have a reed valve on engine breather to minimize crankcase pressure. Mikes SX 650 and others do a good job and if you don't have one that may be what you need to stop that leak.

Primary leak. Did you use a new rubber seal? If yes others will have to suggest something.

swooshdave said:

One thing that can help the engine leaks is a good breather.

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Thanks to all the great information here, I did install an additional reed breather to the timing side. I suspect some oil gets past the tack drive seal just from spinning and torque.

Here is the seal I used for the kickstart. It was cheap enough that I bought a few of them.

http://www.ebay.com/itm/CR-SKF-Chicago- ... 2eb07b95a6

As for the primary, this is a good spot to get out your high temp RTV. Pull the stock gasket, run a bead of RTV in the groove (don't fill it). Put the stock seal back in, gently bedding it in the RTV. Now tighten the outer case into place enough to force excess RTV out of the groove and seat the seal. Don't tighten it down completely, leave a turn or two on the bolt. Now let the RTV set up. Clean away the excess. What you have now done is formed the gasket to your case. When torqued down it should provide a better seal.

And yes on the tach, you might as well get it machined for a proper seal. http://www.oldbritts.com/11_065200a.html

Russ

rx7171 said:

I'll assume the bush behind it is not worn, since if so the shaft would move too much, making a seal difficult.

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I did not replace the kick start bushing with new. I will. good advice, especially since I get the feeling kick starting with 10:1 compression is tough on it. I weigh 190lbs and it stops me mid kick sometimes. That's a lot of torque on that bushing and seal. :shock: