Oil in my Isetta rear drum

[Bob Purton]

I'm asking this on the rum forum because the Isetta one appears to be up the creek at the moment.
I keep getting small amounts of oil finding its way into my rear brake drum, I have changed the oil seal, tightened the splined shaft nut, new gaskets etc but the problem persists, any ideas? Whilst we are on the subject what the channel in the seal holder for? It looks like it should vent something but as there is a rubber seal washer sandwiched between the oil seal and the brake back plate I cant see what its for. Who can enlighten me please?

[Jonathan Poll]

I'm asking this on the rum forum because the Isetta one appears to be up the creek at the moment.
I keep getting small amounts of oil finding its way into my rear brake drum, I have changed the oil seal, tightened the splined shaft nut, new gaskets etc but the problem persists, any ideas? Whilst we are on the subject what the channel in the seal holder for? It looks like it should vent something but as there is a rubber seal washer sandwiched between the oil seal and the brake back plate I cant see what its for. Who can enlighten me please?

Hi Bob,

  When I was doing the rear brake drum on my Nobel, we had 2 of the main shafts connected to the drum. One of them was quite bad. I'm sure yours is OK, but is there maybe a scratch, big enough to let oil dribble through the oil seal?

Jonathan

[Bob Purton]

Hi Jonathan. That's a very sensible suggestion. The surface looks pretty smooth though so I would be surprised if it were that. I reassembled it all this afternoon with a new seal. Dave Tadman suggested I use slightly less oil in the chaincase and perhaps try a thicker oil. We shall see. One thing I will say is that I took it out for a spin for the first time with its new Radial tyres and boy does it improve the ride and steering! Its like a different car!

[Big Al]

Allegedly they are easier to turn over on Radials. I assume this is due to better grip and the tyres not breaking away as crossplys tend too on the limit. Radials transform Goggos too.

No idea on oil contamination but I have cured weeps on clean, but in fact smoothly worn, shafts by using a double lipped seal. (Mine come from the Farne Isles. Sorry). This either works as the other lip is running on virgin metal or that there are in fact two barriers not one. Who cares if it solves the problem. If the Isetta is like the Schmitt it has a breach for another component, brakes in the Schmitt, which has an inadequate oil sealing arrangement. Somewhat frustrating.

[Bob Purton]

I will let you know if I roll it but as my name is Bob Purton and not Jeramey Clarkson its unlikely.  For my driving style I think the benefits of the radials outway any alleged down side. Good to know though Al. Thanks.

The seal is a double lipped one. Another theory I have heard is one of pressure build up in the chain case venting off at the weakest point. Not sure about that.

[Big Al]

I am sure you will not fall over but if it were me I would be in a car park experimenting for feel as I have a habit of pressing on a bit. I like to know the limits and what they feel like. To Trienkel owners I would say be careful if you do this. Once met the boarder between cornering and rolling is marginal! The Schmitt on the other had is very recoverable. Only reflects the differing markets the cars were responding to. The Schmitt is much more an enclosed bike whereas Trienkels and Isettas are small cars I feel. That is why the ownership demographic is subtly different and why I tend to Schmitts.

That can only be pressure through heat generated so if it is leaking on short runs that seems unlikely. I would be surprised if the unit is not vented somewhere even if it is a deliberately loose fitting somewhere on the upper area of the assembly. The 'Schmitt vents through the rear brake cable access.