Mine has developed a leak over the past few months... dripping a few drops after every ride. I have everything I need to service it next week, but I'm wondering what the usual culprits are, causing them to leak?

With only 18,000 miles, I would hope the shaft and bearing are in good shape... what are some other causes?

 

For me it was the inner primary seal behind the clutch hub, was an easy fix, on my friends bike is was the shifter seal on the tranny, this also was an easy fix while the primary was off

 

Mine was the trany seal, very easy fix but you will need some large sockets for the compinsator and clutch basket.
Mine was most likely over filling the tranny is what I was thinking, but not realy sure.

 

I checked it out yesterday, and it'd definitely the inner primary seal. Could an improperly adjusted belt or inferior fluid have been a contributing factor?

 

Possible certianly, but seems unlikely. You sure it's only the seal? Did the seal lips look damaged? You sure the race didn't walk into the primary slightly? The op seal seals on the race, of course, not on the output shaft proper and if it fails & moves inboard - big leak. That's what happened to me.

 

Mine's not apart yet, doing it this week. I just want to have a list in my head, of things to look for when I tear it down. I did read in the manual, that there is a specific range for the depth of the seal, in the bore.

Since I'm going to have it apart, how long are these drive belts supposed to last, with proper maintenance?

 

Inner primary leaks are pretty uncommon on 06-up bikes. The 5spd bikes had big problems with the shift shaft seal, which was fixed for the most part on the 6spd bikes. It's most likely just the mainshaft seal in the inner, you should be able to tell once you get it apart. Compensator is 13/16, clutch hub nut is 30mm. Get new inner primary bolts. O ring for starter too, I've had those leak. If the shift shaft seal isn't leaking leave it alone. It's a pain to get out and you're more likely to gouge the shaft or case trying to get it out and cause a leak rather than prevent one. I'd replace the inner primary bearing and race while you're there.

The belt will last a very long time with proper adjustment and if it's clean. Lots of rain and dirt roads will cause it to wear faster. Now would be the time for a front sprocket if you've ever considered a gearing change though.

 

On mine it was the large seal behind the pulley. .not sure what caused it though the bearing(s) were in good shape.

When you're in there you'll look at the following:

Inner Primary seal (on the inner primary case)
Main drive gear seal (small one, behind the race on the mainshaft inside the main drive gear)
Main drive gear seal (big one, behind the pulley)
Shifter shaft seal
Starter O-ring which seals to the inner primary. .it's attached to the starter.

Look for obvious signs of leaks at the easy ones first (like the inner primary). The large MDG seal you can't access without some work (removing the pulley) which you'll want to avoid if you can.

Even on 6 speeds that race walks into the small MDG seal and takes it out. Some people go in for a leak and find their MDG large roller bearing is toast without noticing odd noises. Hopefully that's not the case.

 

I run Harley oil in the primary (basically clear) and Redline Shockproof in the Tranny.

Its a great way to tell what's leaking as you either get clear or red drops of oil.

Unfortunately I have small pools of both colours under my bike at the moment, so I now have my first winter project define for me...lol.

 

Thanks for the tips, guys. It's definitely dripping down the primary case, from behind the drive sprocket. Bike has 18000 miles, so I was hoping it was not going to need a new bearing, but I'll check it's condition.