Oil leak from rear shaft hub

1985 XJ700N. I just noticed that I am getting an oil leak from the top of the rear hub around the round cap--I assume that is a relief vent. The cap is on tight and I haven't tried to remove it. Any idea why that may be happening? The oil is clear and I haven't checked the rear end oil recently, but I did when I got the bike abour 10,000 miles ago and would have notice if it was over filled.

 

The final drive is venting normally. Even when full it will tend to spit out gear oil when warm. Eventually the venting of oil will stop, the level will be lower, but there will still be plenty of gear oil in the final drive.

 

That's good to know. It is just the first time that I have noticed it actually dripping on the concrete.

 

It is still leaking--or spitting as k-moe says. But it's enough to get on the tire. At least I know it's not out of oil, but it sure looks excessive to me. Any thoughts?

 

Is the oil definitely coming from the breather. I ask because on my XJ650, an internal oil seal had failed/been fitted the wrong way around and oil found its' way on to the rear wheel as per the above photo.

Surely, with the correct oil level, oil shouldn't be coming out of the breather. I've never experienced this in 42 years and 59,250 miles.

 

Is it possibly coming out of the drain hole below?

 

That pic is NOT normal. The most seepage (XJ750 Seca) I've seen is just enough to get the cap and surrounding area 'road grimy.' I'd clean/degrease everything (esp that tire) and try to see where it's actually coming from. If it is the seal inside the hub, it's hard for me to imagine it getting all over the outside of the final drive like that, but there are a lot of forces at play (gravity, wind, rotation, etc.). Were it me, I'd start by pulling the fill plug and verify it's not grossly overfilled (though I'm not sure how that would be managed), or by this point, getting low. Then I'd pull the rear wheel and check that seal. I definitely wouldn't put a lot of miles on it like that. Just me, though.

 

I removed the rear wheel on my XJ650 and there was oil in the hub of the crown wheel. The centrifugal force must have been sufficient for the oil to get past the o-ring on the wheel splined (male) part and on to the wheel/tyre. This o-ring is just a grease seal. Oil should not be present here and can only have come from the failed oil seal behind the crown wheel needle roller bearing. On examination, (as above) the oil seal was fitted incorrectly when the final gear unit was previously overhauled with all new bearings and seals. Now having to have the final gear unit partially repaired again.

 

Those rear gear assemblies can be had for a song and a dance. Part # 5G2-46101. Probably easiest to just find a replacement.

 

I'm in the UK where replacement final gear units are not as readily available as they are in the US. I did manage to pick one up which has been fitted to the bike and used this year. What does bother me is that the oil, when drained is contaminated. It's not clean and has a black discolouration which I don't understand what is causing it. This is the same as the original unit which I had overhauled whilst the parts are available and someone to do the job although not correctly. My objective is to have the original unit rebuilt as a serviceable spare. Secondhand units are an unknown quantity.

 

@tabaka45 Wow that is alot, you sure it's not overfilled or has the wrong (lighter weight) oil in it?