Ok, so I've got this 1990 K75S that I'm resurrecting. Several threads about the electrics elsewhere. But the other day along with my other projects God or his angels made me question if the tranny and final drive were properly lubed. I had just turned it on and wondered if all the driveshaft was properly lubed. So I checked. Tranny looked Ok, but when I opened the final drive/rear end I was gob smacked to see the color of the lube was orange and bubbly. Looked like water to me. How the rear end got water in it is beyond me or this thread. But there it was. So I went down to the shop and bought a quart of 80/90 lube. 

Now Here is where I would appreciate your criticism and suggestions. How to get the bad fluid out. I opened the final drive and let it drain. Definitely water. But being a worrier I wondered if that was sufficient. So I got a spray can of WD-40. Don't know if it is known by that name outside of the US. But I closed the bottom drain hole and sprayed most of the can into the final drive. Then I turned the bike on and with it on the center stand I spun up the rear wheel. Then I drained the WD-40 into a separate container and looked at it. Didn't look particularly bad but I'm still letting it drain for an hour or so. 

My question, in your opinion is that sufficient to clear any lingering water out of the system? So that I can refill the final drive.

thanks for the attention
J.

Good job flushing with WD-40! Letting it drain longer is smart. You could also use compressed air to dry it out completely. Once it’s dry, refill with the 80/90, and you should be good to go. Glad you caught it early!

jjefferies wrote:How the rear end got water in it is beyond me or this thread. .

It isn't as mysterious as crop circles. 

One of the ways water enters engines, transmissions and rear drives is as condensation that can occur during long-term storage in varying temperature and humidity, or persistent short-term use insufficient to fully allow for warmup and evaporation.

Be sure that golden liquid you're about to pour in to replace the old treacle is rated Hypoid GL5 for helically cut gears.

Two Wheels Better wrote:Be sure that golden liquid you're about to pour in to replace the old treacle is rated Hypoid GL5 for helically cut gears.

"Two Wheels..." send me running to the garage to double check. But yeah GL5. Thanks for making sure I didn't royally sc*w it. It's been my day

J.

The WD-40 should have done the trick. When I was rebuilding Kostenlot, the engine that Paul sent me (thanks Paul! Again and again and again!) was a bit dusty from long-term storage and missing camcover D-gaskets. I emptied half a large can of WD-40 into the engine's nooks and crannies, replaced the crankshaft cover and left it sitting on the crankshaft cover overnight. Following day, the puddle of WD-40 had not only obviously removed the dust but it had also brought out some loose combustion products with it too.