’48 Panhead - Oil Sumping – cured – TIP

[harleygreg]

Much has been written on the subject over the years, so here is my solution.

The problem is usually the check valve seat not matching the ball bearing to seal the oil flow, so when the bike is left not running for some time, oil seeps past the ball bearing seal and ends up in the sump.

In order to seat the ball effectively, the pump body needs to be removed.

See image - The treaded bearing of the correct size is available on eBay. You can attach this to the threaded section of a long bolt and then use a hand electric drill and valve paste to seat the ball. Works well.

Thanks

Greg


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[T. Cotten]

That never worked for me, Greg,..

When I actually tested the seats,

CHEKTEST.jpg

It made it worse!

https://forum.antiquemotorcycle.org/...ing-challenges

....Cotten

[duffeycycles]

In a former life,I designed filler nozzles for liquids.I think making the seat wider gives less pounds per square inch of pressure on the seating surface.The spring strength needs to not change.The original seat is a taper & ball with very narrow seating area.Making seating area wider is the wrong direction as Cotton keeps pointing out & many others have tried.The angle of the seat is also important so it does not bind/lock in place.

[dukekleman]

Yes, you gentlemen are correct. A widened ball seat area changes the spring rate effect greatly. This will compromise it's sealing abilities. Also be careful of an interference angle as mentioned.

[joe fxs fxr]

You can also use a push rod and lapping compound, rolling it back and forth between your palms. IDK about the old pumps, but the aluminum ones use a 3/8 pushrod out of an EVO or Twin Cam.

[T. Cotten]

There's only about four pounds of spring pressure, Folks...

A full re-cut of the seat doesn't change it that much.

Those of you who re-cut motor valve seats know the wider the seat, the harder it is to achieve a perfect seal. A ball dropped on a hole or conical seat would ideally make contact at just a circle of points, and leakage would depend upon the machined finish. (Graciously, oil molecules are large.)

As I have posted previously, using bubbles to judge leakage, the best seal was achieved with a simple flat-grind to remove any wear, and any further dressing made it worse. I suspect the factory just poked a hole and let the ball seat itself.

.....Cotten