Oil leak. Cause?

[Ventodue]

Hi All,

My Vento has started peeing oil out from behind the final drive sprocket. I haven't taken anything apart yet, but is this likely to be the seal(s) highlighted in red here ? (P.s. The gear assemblies of Bologna and Barcelona bikes are the same).



If so, is it possible - as I know it is on the twins - to simply stuff in another seal? Or does the blessed thing need to come apart?

All thoughts appreciated!

Craig

[Bevel bob]

Hi Craig, There is a bearing (orriginaly unsealed) with a pen steel washer between the bearing and case. I left out the tatty washer and fitted a bearing with an outer seal. This did not do the job ! ,and I wished I had left the washer in!. I suffered a leak for some time before I realised that with a little less oil in the sump the leak would become insignificant. As I don't do big milage and check the oil ,which stays at the level its not a problem. This is on a narrow case which has significantly less reserve than the later motors.

[Jon Pegler]

Hi Craig,

Your 'seals' , highlighted in red, are not seals but horseshoe circlips to hold the various gears in place.
To cure the leak behind the sprocket you need to split the cases and fit a new 2RS sealed bearing inside the case.
Although not ideal, it is possible to fit a new bearing into the right hand case by removing the head and barrel,timing cover and gears and splitting the cases without disturbing the clutch/alternator.
I would only recommend doing so if you are sure that the shimming of the rest of the motor is to specification to start with.
You also need to ensure that any centre gasket is the same thickness as the old one.
I had to do this on a couple of motors that were newly re-built and re-shimmed but had bearings that had faulty seals fitted to them.

Jon

[Ventodue]

Thanks Bob, Jon. (Yeah, I see now - from the drawing in the Haynes manual of all places ! - that those are circlips, not seals. My bad. A misinterpretation of anello elastico, plus a large dose of wishfull thinking based on the twins ...).

Rats ...

This one, Jon? I guess I should do the one on the other side at the same time ... Anything else I should consider changing while I'm there? The bearings on the other shaft?

[Ventodue]

A little update. I may have found the cause - and therefore the solution. The breather tube was collapsed/crushed. Just above the breather itself, so completely obscured from view by the frame .

5 minutes work with a hairdryer and a bit of steel tube and all is open again. At least temporarily, while awaiting a more permanent fix.

So will put everything back together - had to remove the battery and other associated junk just to get to the breather - and see what gives ...

Fingers crossed .

[graeme]

Hello Craig,

In Australia there is a discount auto part supplier called Super Cheap that sells radiator and heater hose in various sizes and bends.
I found some heater hose bend profiles (preformed) that suit the tight bends from the breather that clear the battery tray etc.
These hoses won't kink after time and provide an easy cheap way to get around the obstructions.

Graeme

[Ventodue]

Yeah, good thought Graeme -ta. Am going down a similar route ...

[Jordan]

Widecase breather hose has to squeeze past a frame tube and the battery tray, but should be almost a straight run otherwise.
How come a bend is needed?

[Ventodue]

How come a bend is needed?

I'll see if If I can take a photo ...

[Ventodue]

How come a bend is needed?

I'll see if If I can take a photo ...

Right, here's the breather pipe arrangement that I inherited with this bike ! In the photo, the brown pipe is now straight. But before I heated it up with the hair dryer, it was bent over double where I've put the arrow.



The extension piece of braided pipe has now gone and been replaced with a longer length of uncrushable tube that goes all the way down to the breather in the crankcase. Hopefully, that will do the job. If not, I'll have to swing the engine down to do the job properly. That wormdrive clip is inacessible otherwise.

Now just waiting on a delivery of bits from Spain, including a new gearbox sprocket, before I can road-test.