1939 ULH Scavenger Pump

Not returning oil adequately

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39Kicker
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1939 ULH Scavenger Pump

#1

Post by 39Kicker »

I am not getting good return from my scavenger pump. It just drools a bit not a nice little spurt like my PanHead. Probably too much oil is staying in the lower end. Is there any outside adjustment that can be made to increase return? I am running open so the chain oiler is capped. Does the chain oiler adjuster also increase the return flow ?, wishful thinking.
RUBONE
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Re: 1939 ULH Scavenger Pump

#2

Post by RUBONE »

Don't try to compare the UL system to a Panhead. The UL is operating on about 1/2 the volume of the OHV. If your system is timed correctly, the flapper valve good, no excess oil out of the breather, proper feed pump gaskets, then the system will be OK and the return will be a steady drool.... :shock:
39Kicker
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Re: 1939 ULH Scavenger Pump

#3

Post by 39Kicker »

Thank You Very much Rubone It seems to perform well. I just finished a ride and checked the amount of oil in the case's with a cable tie about an inch or so with this crude method not nearly puking out the vent. Guess I need to relax a bit and enjoy the Flatty experience seems they are pretty reliable.
pan50head
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Re: 1939 ULH Scavenger Pump

#4

Post by pan50head »

Two friends and I planned to go on a long trip in hot weather riding our big-bore flatheads. They had recently rebuilt their engines but mine had been running for a while, but not on a long trip. To test out their rebuilds, they rode them 300 plus miles in a day. Both engines died because of lack of oil. After some research, they discovered the cause to be too thick of a feed pump gasket. They got the gaskets from VTwin and they were .008. They determined that NOS gaskets were .002. Mine was not as thick as .008 but I installed an NOS gasket anyway. We did our 2,000 trip with no issues. Our conclusion was that putting around town was not a problem, but hard riding all day in hot weather was a problem with the thicker gaskets. Just my 2 cents.
chuckthebeatertruck
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Re: 1939 ULH Scavenger Pump

#5

Post by chuckthebeatertruck »

Yes, this freaks out almost every single new flatty owner.

The dribble is normal. Even if you move to a four vane pump and increase the volume, it's still pretty pathetic.

Put simply, flatties don't run on much oil and don't need to. The main and rod bearings prefer mist to flood, so there's enough oil to do that. Pistons and top rings suffer, but keep going.

It seems many bikes hold a couple ounces in the case after a run. Don't freak, it's not an issue.

But, the overly thick pump gaskets ARE a known issue. Fish paper gaskets only, unless you enjoy problems.

Basically, a pocket is created that whilst tiny, greatly affects the volume pumped.

All of this means your oil tank never quite gets hot like on ohv twins, and that too freaks new owners.

Keep in mind pre-war motor bicycling was a hella different animal.
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Re: 1939 ULH Scavenger Pump

#6

Post by Larry »

The rotor stands proud of the pump body, typically by .003". This dimension should be measured before installing any gasket.
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Re: 1939 ULH Scavenger Pump

#7

Post by kitabel »

What part of the rotor, and what part of the body?

Have you had the body apart or the cover off?
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