leaky gearbox mainshaft

[Steve]

I have a slight to not so slight problem with oil leaking from the gearbox mainshaft on my 1936 flyer, I am sure it is a common problem but not one I have had to deal with myself before so I would greatly appreciate the advice of those more knowlegable than myself, many thanks
Steve

[chstorm]

First a (maybe silly) question: Have you filled oil up to the correct level? There is a hexagon screw in the front end of the r.h. side of the gearbox, -an oil level plug. Before filling with oil, you unscrew this plug. If oil is running out, you have filled too much. Else refill until oil comes out of the hole, and let it run until no more is coming out. Then refit the plug. I had an oil leak from the gearbox on my ’36 flyer, and discovered that the oil level was too high. With the correct level – no more leak! You also need to use a sufficiently heavy oil. A SAE140 straight (no hypoïd) gear oil (Shell Dentax) is OK. It has a “body” similar to a SAE 50 monograde engine oil. If the oil is too thin, it will splash about a lot more than a heavy oil. Personally I use Castrol R40, which may sound a bit exotic, but it adheres beautifully to all internal surfaces in the gearbox.

If this does not help, it is possible to fit a modern oil seal. I have had that done on my ’38 flyer in connection with a recent gearbox and clutch overhaul. I am certain that Roger Moss, who helped me, can steer you in the right direction.

Kind regards,

Carl

[Steve]

many thanks chstorm will contact roger

[Erik]

My Flyer gearbox also has a seal fitted and does not leak a drop.
So it might be a worthwile conversion.

Erik

[pplatt]

Hello again Carl,

I probably ought to check my gearbox oil level too & its a job I can do while I’m waiting for my new primary chain to arrive in the post!

Could I just ask for a bit of clarification; Is the gearbox oil level plug the one on the right hand face of the gearbox towards the front of the ‘box? On my bike it is tucked in tight behind the foot rest so I can’t get it out without moving the footrest. Does that sound about right? 🙄

I gather the bike needs to be on its wheels (and presumably as close to vertical as possible) when checking the level.

Cheers,

Pete P.

[chstorm]

Hi Pete,

The gearbox oil level plug is indeed the one on the right hand face of the gearbox towards the front. It is indeed tucked in tight behind the foot rest, so you have to loosen and move the foot rest to gain access.

The bike should be positioned vertically on both wheels when checking the oil level. Correct oil viscosity is straight gear oil SAE 140 (not hypoïd oil). Shell Dentax is ideal, if you can get it, but any straight SAE 140 gearoil will do.

Cheers!

Carl

[pplatt]

Marvelous. Thanks Carl. I think the box has straight 40 in it at them moment so I’ll probably stick with that. I has been rebuilt and fitted with modern seals so leaks shouldn’t be an issue. The oil level is most likely fine but I want to learn how to look after the old girl properly!

Thanks again.

Pete P.

[Author]

Posts