Want to get opinions before tearing into it. Final drive leak

[Guest]

I'm on 82 650gl and I'm having a problem with an intermittent leak in between the rear rim and final drive. The only problem though is this leak only occurs while at highway speeds for a good 10 miles or so then covers the rear tire and stops whenever I stop or slow down to backroad speed. I never have any leaks while the bike is sitting and I can drive it all day long on backroads 30-40 mph and not a single drop comes out. It's only when I get on the highway and stay at 50 mph or more for an extended period that any oil comes out. I've read there's some kind of breather that can possibly cause this problem if there's too much oil but not entirely sure that's my problem because the oil level is down 1/4 inch or so below the threads on fill hole. I don't think it to be seals because I'd think seals would leak at all times not just at higher speeds and it doesn't even do this at all times just here and there. If you have any info as to what could be causing this intermittent leaking please let me know so I don't go to tearing into stuff I don't need to lol I hate messing with that back tire lol. I'm also going to change the oil in the pumpkin again any advice on what could be used as a sort of flush before adding new oil?

[fixmybrokecomputer]

I wouldn't think you'd really need to flush it. Just don't turn the rear wheel as you're filling the final drive as it would make it easier to over fill. Before I tore into a final drive, I'd just pick one up from a forum member or ebay.

[leftlostcommonsense]

Other than the occasional leak I don't think there's anything wrong with it. Any idea if there's possibly some kind of breather inside of there that could get clogged and cause it to leak? I've never torn into one so I have no idea what's inside of there I just seen bikecliff mention there being something like that in his 850 that would leak if filled up all the way to the threads. I have no idea about the 650 though.

[Cipher]

yes there is a breather circuit. Id drain and replace fluid. I do know diff grease can congeal woth age and effecyively plug things. Its almost like a jelly.

Maybe you can rinse out the circuit with a bit of solvent and then drain and refill to spec.

14-12 pf the manual on basscliff website.

[Cipher]

yes there is a breather circuit. Id drain and replace fluid. I do know diff grease can congeal woth age and effecyively plug things. Its almost like a jelly.

Maybe you can rinse out the circuit with a bit of solvent and then drain and refill to spec.

14-12 pf the manual on basscliff website.

[tom203]

Seems odd to just leak at high speed. Me, I'd gamble on another unit off ebay like this...

https://www.ebay.com/itm/1981-SUZUKI-GS650GL-GS650-FINAL-DRIVE-SHP/201657673707?hash=item2ef3bbe7eb:g:Z54AAOSwcBhWXMiE:sc:USPSParcel!04029!US!-1

[Cipher]

Seems odd to just leak at high speed. Me, I'd gamble on another unit off ebay like this...

https://www.ebay.com/itm/1981-SUZUKI...el!04029!US!-1

That is much cheaper than a BMW! One assumes that the leakage is caused by air pressure building up due to heat building up. But happily a few hard runs and the problem goes away. just like a leaky fork seal.

[leftlostcommonsense]

I went ahead and changed the fluid yesterday haven't had time to take it out and see if it still leaks yet. The fluid i drained only had possibly 2-300 miles on it and it was pretty black. My guess is whoever had the bike before didn't change that fluid much at all and the fresh fluid I put in a while back was dirty due to it cleaning out the residue of the old stuff that was left. Guess only time will tell. They're cheap enough to replace if I need to. As for the breather circuit inside of there is there a hole on the backside of the pumpkin that should be checked for blockage or cleaned out?

[Cipher]

if you could refer to 14-2 of the manual you would see the circuit. Top hole is for air. Hell flush it backwards with a mild solvent and see what drip out.

[leftlostcommonsense]

I appreciate the help. Thank you

[bwringer]

Yep, there's sort of a winding path for air to vent as the final drive heats up (this is called a "labyrinth" seal). I'd bet this is clogged.