Weird leak from driveshaft/diff connection

[Courtney]

I sold my bike to a really nice guy and he sent me this pic of a leak it has developed . I can't figure out why it would leak at the top of the gasket area, but obviously it is. Would really appreciate any experienced guys giving me an idea of what could be causing this weird leak. This was the amount after a 40 mile ride yesterday. Thanks folks.

[3Phase]

I sold my bike to a really nice guy and he sent me this pic of a leak it has developed . I can't figure out why it would leak at the top of the gasket area, but obviously it is. Would really appreciate any experienced guys giving me an idea of what could be causing this weird leak. This was the amount after a 40 mile ride yesterday. Thanks folks.

I can't help thinking about that old airplane inspection joke:
Problem - Evidence of leak on right main landing gear.
Solution - Evidence removed.

....

Let the new owner borrow your "Easy Button" and have him check the torque on the four nuts that hold the Final Drive in the swingarm. The torque is 30.4 ft-lb (4.2 m-kg).

If the nuts were loose, that should fix the leak and he's done!

Do not overtighten the nuts. Even a small amount of extra torque will distort the aluminum Final Drive housing and it can ruin the drive if he chimps out on it.


If that didn't work and he's determined to fix the leak, now would be a really good time to loosen the filler plug and the drain plug in the Final Drive but don't drain the oil yet.

Remove the rear wheel, take off the four nuts holding the drive in the swingarm and remove the Final Drive.

Set the Final Drive in a drain pan and remove the drain plug, then go do something else for a while.

Wipe the drive clean, then remove the Phillips screw that holds the Input Assembly in the Final Drive.

Even if he drained the gear oil, have him keep the drive 'nose up' so he doesn't dump stinky gear oil while he pulls the Input Assembly out the housing. The Input Assembly can be difficult to remove so tell him to be patient and slowly work it out of the housing.

When the Input Assembly is out, the shim stack and the mating surfaces of the input Assembly and the Final Drive housing have to be cleaned.

Have him spread a very thin coat of his favorite sealer on the input and final drive faces, and all of the shims in the shim stack, then put the drive back together and fasten the Input Assembly in place with the Phillips screw.

Wipe off any sealer that oozed outside and hope that it didn't ooze inside too.

Clean and grease the driveshaft and coupler splines while he still has the drive off of the swingarm.

Put the Final Drive back on the swingarm and put on the four nuts but don't tighten them yet.

Put the rear wheel back on and torque the axle nut to 108.5 ft-lb (15.0 m-kg) and the pinch bolt to 4 ft-lb (48 in-lb or 0.6 m-kg).

Now that the aluminum Final Drive housing has been aligned and preloaded by the rear axle, torque the four Final Drive nuts to 30.4 in-lb (4.2 m-kg) to seat it in the swingarm and wipe off any more sealer that oozed outside.

Let the sealer cure while he checks/refills the gear oil in the Final Drive.

Go for a ride!

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[Bonz]

What not just take the bolts out, clean the surfaces and put some Yamabond or similar on it and tighten back up? It's the leak that is the issue, correct?

[red bandit]

Are you sure it's not the shock leaking and dripping on it? Just a thought.

[3Phase]

Bandit, that's an even better, easier fix than torquing the nuts.

What not just take the bolts out, clean the surfaces and put some Yamabond or similar on it and tighten back up? It's the leak that is the issue, correct?

Bonz, I told him to have the new owner torque the nuts first. That will probably fix the leak and no one will have to dive in with the sealer or bail and let the new owner deal with it.

There are no bolts, it's studs in the Final Drive with nuts to hold it in the swingarm but other than that it's pretty much exactly what I told him to tell the new owner to do if torquing the nuts doesn't stop the leak.

It's easier to pull the rear wheel, then the drive. You can try to loosen and move the the drive far enough away from the swingarm on the studs to clean the oil out of the shim pack and off the mating surfaces so you can add sealer but it's not a good idea.

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[Bonz]

I meant nuts...

[3Phase]

I meant nuts...

There is a Phillips screw holding the Input Assembly in the Final Drive housing.

The most you could do without removing the rear wheel is pry the drive away from and probably bend the swingarm to add sealer between the Final Drive and the swingarm. There is no fluid in that part of the drive train so it won't fix any leaks or do anything else useful, really.

You have to remove the Phillips screw to pull the pinion assembly and clean the shim stack and the mating surfaces. Add the sealer of your choice -- Yamabond -- then put it back together and tighten the Phillips screw.

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