October 2000 Tech Talk
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1948 Aluminum Oil Pumps

From: "PAUL HANES" <hanes.eng@xtra.co.nz>
Does anyone know what the clearances are inside a 48 oil pump? Clearance between shaft and where it runs in the middle of the pump body? Has anyone tested these pumps on the bench? I tried mine by running of a bench drill at 1500 rpm and the return pump works real good but the feed seems slow, and when I stop the oil getting to the return pump the feed sucks air so must have to much clearance where the shaft runs in the housing.´ When the pump is on the bike the oil is going around ok. I work on gear pumps all the time on forklifts but they are far better sealed than the Indian pump.

From: Michael Breeding <mbreeding@cnsp.com>
Bob Hoyt, 970-482-0354 work, manufactures aluminum oil pump gear bodies, covers, and shafts to fit his bodies. There is one set on my '51 bobber and it works very well. Not cheap. Call him for more information.
Michael Breeding

From: "PAUL HANES" <hanes.eng@xtra.co.nz>
Thanks Michael. Does he have a email address or fax # ? I have 1 to 1-1/2 thou between gears and face which I think is ok. But I have 3 1/2 thou between shaft and housing which I think is the problem, it can and is sucking air.

From: Michael Breeding <mbreeding@cnsp.com>
You need to call him. Yes, the problem is almost always between the shaft and housing.

From: Patty Duffy <MICHIGANDER@worldnet.att.net>
Hi Paul
I know you have got much good info by now, but to have .0035" on the pump shaft through the pump housing would be far and away too much and would be a very sloppy fit when putting the pump together. If that is what you meant by shaft fit.You may hand lap the cover to a flat condition be for assembly for better pump action and of course a new set of gears would make a difference if the old ones show much wear. When you assemble to test, 1000 rpm will give a decent pump speed to test return OR input. To check the input without the return side squirting oil all over you after the pump is primed, you can for a very brief time cover the the return line to your oil source with your finger, the input side will still function. The best test for the pump is to mount on a cam cover if you don't have a test stand made and have a decent supply of oil in a return in a small tank and a second tank to take the return oil which is pumped out. Then make a small supply tank and mount above the supply fitting on your pump, spin away! Remember the input flow will be slow but IF you measure the amount in the input supply  tank then you can check the flow out of the cover over a three min time. The return operates on at least a three to one basis.

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