V65c Bevel Box oil leak

I run a V65c and recently fitted an output shaft oil seal and the spacer it sits on, I ran it for about 30 minutes to make sure it was oil tight before completely re-assembling the bike .
I did a couple of runs totalling about 300 miles in all before I noticed a bit of a drip underneath the rubber gator covering the drive shaft , my first thought was the seal had gone again so removed the swinging arm and bevel box from the bike there was oil inside the swinging arm just in front of the bevel box also a small amount where the shaft exit’s the gearbox so I was unsure where it had come from.
I checked the gearbox oil level which appeared to be ok then checked the bevel box level which is below what I expected so I am assuming it is the bevel box oil seal that has failed , but has anyone experienced a pinion shaft oil seal failure that leaked oil up the tube to leak from the rubber boot ?. Jack

Can’t see how the oil made its way back up the shaft. I suspect you have a slight weep on the gearbox output seal. You would have to loose a lot of oil to notice a loss of oil from the gearbox. Never had a leak from the pinion shaft, is the breather clear. The bevel box oil level needs to be cheacked with the swinging arm horizontal. I remove the shocks and use a spirit level on my V50.

I first thought along the same lines you have , but the gearbox oil level is fine (checked it again) the bevel box however is down quite a bit.
I ran the bike in 5th gear for 30 minutes or so until the gearbox was warm and the engine was at running temperature and kept an eye on the output shaft oil seal nothing came out , the gearbox breather is clear with no obstruction I even blew into the gearbox breather pipe to try and create a bit of pressure and still nothing leaked so I am going to run the bike with the bevel box connected to see if the oil does run up the tube, I will raise the swinging arm to level and see what happens if it does leak I have left off the rubber gaitor so it should point to either the bevel seal or gearbox seal time will tell.

If you drain the bevel box and then refill with Bel-Ray, which is red, it might also give a better clue.

Good idea.
If all oils were a different colour for engine, gearbox, and bevel box it would be easy to determine where the leak was

We put different dyes in all the various oils at work, but they only show up with a UV light.

It’s a trick we use out in BSA land, where there are always leaks and you’re trying to find where it’s coming from this time - engine, g/box or primary.

Is there a seal on the pinion shaft? Big blocks don’t have one. The input bearing is lubricated by oil thrown forward by the crownwheel which then runs back through some slots. On my 850GT loop, the bearing carrier was assembled wrong so the slots were closed off. It filled the swinging arm up and even got into the gearbox and raised the level. Also dripped from the gaiter.

I fitted the swinging arm last night minus the rubber boot filled the bevel box to its level and made sure the bevel box was level to the gearbox and then ran the motor for 30 minutes at about 2,5k revs which got gearbox and bevel box warm , I checked for oil where the rubber boot fits and there was nothing to be seen either from the gearbox end or the bevel box end ,however it did take about 300 miles before an oil leak became apparent from the boot, I then removed the bevel box and there was about a teaspoon of oil laying in the swinging arm in front of where the pinion fits in the swinging arm so evidence that oil is being thrown forward and over the course of 6/7 hours riding could well be enough time to allow oil to leak out of the rubber boot.
The oils seals and o-ring are cheap enough so I will replace these and hope/pray the leak is cured .

Have this problem on my 2015 Nevada 750.
Probably due to blocked bevel box breather.

I said in my first post that it was the bevel box oil seal, I should have said the pinion shaft oil seal.
When I removed the pinion shaft from the bevel box housing I noticed on the roller bearing carrier marks where an attempt had been made to improve oil supply to the front roller bearings this aligned up with an internal drill hole at the inside top right of the casing the two flats on the roller bearing carrier were then at the 9oclock and 3oclock position and would prevent the return of oil to the bevel box.
I have refitted the pinion to the bevel box with these to flats at the 12oclock and 6oclock position hoping this will cure it.
Off to Red Row show today and will put a few miles on the V65c time and a few miles will tell if its cured.

Ranton Rambler, thank you good clue in there (flats)

FFS! :astonished:

Yes it can happen. I’ve just replaced all three bevel box seals on my 2015 Nevada 750 after only 15000 miles! See my new post. There was a little oil in the shaft and it had clearly come from the bevel box end. The reason was that the rubber gaiter at the other end had been badly fitted and there had been water ingress leading to some rust on the drive shaft which was enough to cause undue wear on the first input seal in the bevel box. But the main problem at 15000 miles was the large output seal which had failed for two reasons. Before I bought the bike it had been standing in the showroom for a lengthy period and also, the bevel box breather was blocked with rust and swarf and caused over pressure in the box.