1928 Harley JD Oil Pump Problem

[SteveAdventure]

After a day of testing we discovered that no matter what the setting we had nearly the same results. Full open or fully closed with the same result. How does this pump work? Is there a kit available to rebuild the pump?

Cheers, Steve

[gww]

sent ya a message. gary

[Steve Slocombe]

Dear Steve, this is the first year for the throttle controlled oil pump, which works with two tiny pistons and springs set in an operating shaft driven by a cam gear. The stroke of the pistons is controlled by a hinged plate, the angle of which is a function of the throttle opening. I'm told this system is still used in modern hydraulic pumps. This is not a recirculating oil system, so the pump only has to make up engine losses. At 800 miles per gallon this is about 5 ml per mile. You won't see any measurable oil flow from just turning over the engine. The usual problem on these pumps is weak springs or pistons jammed in the operating shaft. The inlet pipe can also be blocked by rust or debris in the tank. Nearly all parts are available.

[pete reeves]

Steve.
If your problem is over oiling, then I think it’s likely that your pump is working as the factory intended it to work on the roads that were available in 1928.The problem is that with the roads we have available today we are running our bikes for longer periods at sustained higher speeds than the oiling system was designed for. The riders hand book says that the pump will pump at full capacity at throttle settings above 2/3rds, and oil consumption might higher than 1gallon every 400miles at high speeds. When running my bike 50 to 55 MPH my throttle spends most of its time above 2/3rds position so the pump spends most of its time pumping oil at the maximum rate. When I first tested my bike at these speeds I found that my oil consumption was more than 1 gallon every 400 miles and the available adjustments made no difference. The hand book says that no adjustments can be made above 2/3rd throttle position. However I found that I could decrease the oil flow rate by installing a longer than standard screw in the left hand side of the pump. I think this screw was used by the factory to set the position of the pump cam plate and was not meant to be altered .So fitting a slightly longer screw deceases the angle of the cam plate reducing the stroke of the pump pistons. Altering the length of this screw will allow you some adjustment, but be careful as too long a screw could stop oil flow completely. I have set mine so that it still uses about ½ pint per 100miles and at this rate I still get a build up of oil in the cases but the breather seems to leak enough to keep the oil at an acceptable level.

Pete Reeves AMCA# 860 Cannonball #34

[pete reeves]

Page from 1929 owners hand book relateing to the oil pump.