Leaking Middle Drive?

[cywelchjr]

I've been finding a small amount of what appears to be gear lube just about right under the middle drive on my bike almost randomly since changing the engine. Now I did determine that I had overfilled the middle drive when I put the engine in, and it still seems to be a little overfull yet.

I think I saw something about there being a venting system and that it will spill out if it's too full? The strange thing is I'm not sure it's really random, but almost seems like it leaks if I have been running it at high speeds and then park it overnight. Like maybe under those conditions it's expanding and then coming out through the vent?

I've got a known good middle drive on my other motor, but I'm wondering how easy it is to change and if there is anything really to get worried about. Should I just keep a close eye on the level and worry if it gets low?

[bikerphil]

If it's leaking into the driveshaft boot, the seal behind the yoke could be shot. Other possible leak points would be the gasket between the MD unit and the engine, the drain plug on the engine, or the vent tube if it's overfilled. The MD unit is not that difficult to change, once you've done it a couple of times ; ) HTH

[TomRodgers]

Awww... your XS is acting like a Harley now...marking its territory!!!! Bad seals rarely cause catastrophic problems... if it leaks a LOT, then would recommend fixing, but that would be something i would do over the winter. just check the level frequently. if it gets low, add to it. my $.02

[cywelchjr]

If it's leaking into the driveshaft boot, the seal behind the yoke could be shot. Other possible leak points would be the gasket between the MD unit and the engine, the drain plug on the engine, or the vent tube if it's overfilled. The MD unit is not that difficult to change, once you've done it a couple of times ; ) HTH

Based on where it's marking it's spot, it's not coming out of the boot (that and the boot is dry), it's marking it right under the middle drive, and not every night (can't tell if it did last night because it rained all night). I keep checking the level, and it seems to still be a bit high (gonna go get a real dipstick this weekend from the dealer I hope), so I'm hoping it's just coming out the overflow if it's hot when I park. I have noticed that the spot seems to be getting smaller, and it's very clearly gear oil. I am using mobil 1 synthetic, but everyone says to use synthetic so that should not be the issue. I guess I'll just wait and see while keeping an eye on it.

[randy]

JAT, but have you checked that the middle drive mounting bolts are tight? I did have that output shaft seal go bad on me a couple of years ago, but when I went to change it I found that it wasn't the seal on the shaft, but it was leaking where the seal body was seated in the housing. The metal ring of that seal believe it or not, is not rubber coated. Go figure. Before driving the new seal home, I spread a little Right Stuff in the groove on the middle drive. It will never (fingers crossed) leak again.

P.S. try not to roll the wheels through the puddle of gear lube, it makes for a wild ride. DAMHIK!

[cywelchjr]

Yep, I double checked all the mounting stuff. It ONLY leaks sometimes at night, never a drop all day long, and even at night it seems to only leak if I have pushed it rather hard and then pulled in and parked without some slower riding first. It is (as best I can tell without a real dipstick) still a little overfilled, so I am still suspecting the overflow, but then what do I know?

[DGXSER]

Typicaly the vent line from the middle drive runs up behind the airbox(if your still using it) and under the tank. The tube runs through a bracket that is bolted down by the bolt that holds the front top mount of the air box in place.

So, if it is overfilled and you push it hard and it does spray out up there and not get a chance to blow off or dry out while moving, it could take a while for it to find its way to the ground. Like over night....

There is a diagram on here of the dimensions to make your own gage. I typically ise a piece of cardboard or paper marked off to the dimensions, not a great tool but works in a pinch. I did this weekend have the chance to use the factory gage and it is MUCH nicer for sure.