revtothelimit - motorbike forum

The final drive housing on my R1150GSA has a very slight leak. Shopping with new crush washers, would PTFE tape or leak sealant/thread sealer be a better option?

Tried be crush washers but they don't do the leak entirely.

Ta.

Which part of the housing?

If it's dropping from the bottom, trace it up to the actual weep.

The reason i ask is that often the gearbox output shaft will weep and the oil will run down the drive shaft and then weep from the bottom of the rubber gaiter, making it look like the final driver is weeping.

If it's the gearbox weeping don't sweat it, the output shaft is higher than the mean level of the oil so it only weeps when in use, which means it won't lose much oil.

Rockburner wrote: Tue Jul 07, 2026 9:46 pm Which part of the housing?

If it's dropping from the bottom, trace it up to the actual weep.

The reason i ask is that often the gearbox output shaft will weep and the oil will run down the drive shaft and then weep from the bottom of the rubber gaiter, making it look like the final driver is weeping.

If it's the gearbox weeping don't sweat it, the output shaft is higher than the mean level of the oil so it only weeps when in use, which means it won't lose much oil.

It's definitely the FD housing, specifically from the drain bolt, all other parts of the swingarm and FD housing are dry. I suspect we've slightly warped the drain bolt hole when we needed lots of heat to remove the FD bearing a couple of years ago.

Have used yellow PTFE and the thread sealer, test will be tomorrow morning riding to the office.

Beancounter wrote: Tue Jul 07, 2026 10:01 pm

Rockburner wrote: Tue Jul 07, 2026 9:46 pm Which part of the housing?

If it's dropping from the bottom, trace it up to the actual weep.

The reason i ask is that often the gearbox output shaft will weep and the oil will run down the drive shaft and then weep from the bottom of the rubber gaiter, making it look like the final driver is weeping.

If it's the gearbox weeping don't sweat it, the output shaft is higher than the mean level of the oil so it only weeps when in use, which means it won't lose much oil.

It's definitely the FD housing, specifically from the drain bolt, all other parts of the swingarm and FD housing are dry. I suspect we've slightly warped the drain bolt hole when we needed lots of heat to remove the FD bearing a couple of years ago.

Have used yellow PTFE and the thread sealer, test will be tomorrow morning riding to the office.

Try a softer crush washer?

I had something similar on the ZXR400 once, i used silicon sealant on the bolt and crush washer, not up the threads, and it worked fine.

Perhaps get hold of some Gas PTFE tape; it's a lot thicker and stronger than the PTFE tape used on water pipes etc.

mangocrazy wrote: Tue Jul 07, 2026 11:22 pm Perhaps get hold of some Gas PTFE tape; it's a lot thicker and stronger than the PTFE tape used on water pipes etc.

If gas PTFE tape is yellow then that's what I've used last night. Drian bolt/hole is still weeping, not as much as before. Back to the drawing board before I shell out £350 for a second hand FD unit...

lol shelling out for something is £1000+ not £30k. You spend that on a round these days

weeksy wrote: Wed Jul 08, 2026 9:48 am lol shelling out for something is £1000+ not £30k. You spend that on a round these days

This is Beanie here, a 3 quid bottle of coke is "shelling out"

If this is a fairly standard drain plug it is not designed to seal via the threads. If it were it would have a tapered thread and there would be some justification for using PTFE tape. It is the annular flat on case and plug flange where it must be sealed. If the surfaces were completely flat and the torque to specification only the type of washer would make any difference. An aluminium washer in good condition would be fine. You could alternatively use a copper washer after softening it by heating cherry red and quenching immediately in cold water. Examination of the washer after use will show whether surfaces are flat and parallel because the imprint on both sides of the washer will be even and smooth.

There are other reasons why some oil might appear including cracks or porosity in the housing. Also have you tried screwing the plug in without any washer to make sure it can travel unobstructed further than is needed and the thread isn't burred over? Could it even be the wrong plug? Final thought is that the design originally may have been intended to seal via an O-ring this would be shown by a 45 degree countersunk finish on the hole.

If I'm not confident about plug and/or casting faces I usually use a Dowty washer which covers a multitude of sins.