1939 UL oil leak

[cuda567]

Bike has been sitting for a couple years…all the oil that was in the oil tank has leaked out onto my lift.
can’t tell where it’s coming from Where should I start?
thanks in advance

[T. Cotten]

Its a natural phenomenon, Cuda!

Gravity makes the oil seep from the tank through the oilpump to the cases, where it escapes through the sprocket shaft 'slinger' into the primary, and then on your lift.

Prevention would have been to drain it before storage; Please do not fill the tank completely before starting the machine, because the lower end is already full.

....Cotten

[pmurray2287]

What dumpster diver said. Additionally, the ball and spring check valve of the oil pump is the culprit. The gearcase can fill up and drain through the breather in the R gearcase.
If the bike does not kick over a hydraulic lock occurs. Oil can find its way into the bottom end not allowing pistons to continue on the downward stroke.

[T. Cotten]

What dumpster diver said. Additionally, the ball and spring check valve of the oil pump is the culprit. The gearcase can fill up and drain through the breather in the R gearcase.
If the bike does not kick over a hydraulic lock occurs. Oil can find its way into the bottom end not allowing pistons to continue on the downward stroke.

They all 'sump' eventually, Folks!

We can blame a worn ballcheck when the cases fill in a month or two, of course, but I found even an NOS pump was not absolute.

(A couple of years is a long time...)

The worst cases of sumping is when a modern sprocket shaft seal has been installed, blocking escape to the primary, and allowing the cases to fill all the way. The motor will still turn through, but attempts to start can be worse than *messy*.

....Cotten

[cuda567]

Thanks for the info guys…much appreciated
Jim Long went through the motor approx 7 years ago and the bike maybe has 500 miles since rebuild
i had the tanks and fenders redone and also redoing handlebars and such so it wasn’t ran for approx 2 years
it does kick over okay..haven’t started it yet
so I’m assuming you guys don’t fill the oil tank all the way and also drain if your letting it sit for awhile?

[T. Cotten]

You can fill it all the way, Cuda,..

After you have purged the lower end.

And yes, I would drain it into a jug if it will be six weeks or more between rides.

Everyone of them sumps at a different rate, but its usually only a real problem if the sprocket shaft slinger overflow is sealed,... most often for a belt drive.

....Cotten

[cuda567]

Thanks for the info…what weight oil do you guys typically run.

[T. Cotten]

Thanks for the info…what weight oil do you guys typically run.

You do know, Cuda,..

Oil questions go on forever!

....And ever.

If Jimmy did sweet motors, then you shouldn't need to go heavy for a few seasons at least.

....Cotten
PS: Personally, I would purge it with a run on 40wt Aeroshell before replacing it with anything with ZDDP. But just because I could.