Oil Pump on Model 50 - how easy should it be to turn ?

The Heavy Twins use a mirror image of the same pump. They have rubber button to seal between the pump output and the timing cover. You have to make sure there is light pressure (around 0.010") on the rubber button when the timing cover is put in place, with whatever gasket will be used. I expect the singles are similar. Am I correct?

My understanding is that the pump should have light resistance when it has been reconditioned, not strong resistance. Traditional practice was to put the pump in place with no gasket or jointing compound. Later machines used a gasket. Just guessing, maybe the faces were less accurately machined? If you are worried, you could use a smear of Hylomar. I don't bother, personally. My Dominator has very good oil pressure when properly hot -45 psi on a very hot day with a few revs up, so it's sound

Paul

Those pumps should be fairly tight to turn by hand - they free up when they're full of oil. As long as it turns smoothly it should be OK.

With respect to the joint with the timing cover, the singles specified a fibre washer. I've thought that the twin type rubber seal may be a better option.

If you use the fibre washer, it should be thick enough to hold the timing cover clear of the crankcase by around .030" so it compresses when the timing cover is tightened down.

As Ian said , the pump should be stiff - when I lapped mine in I was advised that it should be difficult to turn over by hand and indeed it was - like you I had my doubts but there have been no issues in several years . I went the fibre washer route between nipple and timing cover and no issues there either . Don't forget the oil jet and spring upon reassembly .

If the oil pressure is fine then don't touch the adjusting screw. I broke the housing trying to undo mine but was fortunate to fine a good firm to re-weld and tap a new thread. I got away with it!

BTW - should have said - any leak will increase wet sumping.

George

Just found an article on oil pumps, Mike, which states: "The drive gear is keyed to the shaft and only needs 20ft.lbs of torque. The pump body nuts are tightened (no washers fitted) to no more than 12ft.lbs. It also makes sense to replace the old rubber button seal on the outlet feed." He then goes on to explain how he ran it for 15 mins in light oil at low revs to bed in. He then checked the 4 body screws for tightness then centre punched them. It was then dunked again and run in. The article was written by Phil Hannan.

BTW he does note: "Most drive gears have a rounded inner edge similar to the internal gears. It is crucial that these gears are refitted to the shaft with this rounded face away from the shoulder of the dive shaft. Otherwise it will rise up over the shoulder and jam against the shaft housing." You may wish to undo it all and check?

George

There's nothing to it Mike. There are only a couple of interlinking cogs in there.

George

Hi Mike,

This is a bit late now, but quite a few years ago I had a 1951 Big 4 that would fill the crankcases overnight. On stripping I found the pump was free to turn when removed but when I tighten it to the case without the helical gear, I was unable to turn the pump by hand. As the pump body is made from Mazak,I guess the body was distorting and binding against the gears. I never got around to sorting it out as it was easier to replace it.

Regards, Richard.