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

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

Posted by mike_haworth at October 11. 2018

On 1959 Model 50 - just had the Oil Pump refurbished by RGM Norton. However, on turning the drive cog with by hand it seems quite stiff ! I was expecting it to turn over easily and freely. Is something wrong, or is this normal ?

Second point - when I removed the pump in order to send it away for refurbishment I found that, although it is within the engine, a jointing compound had been used when it was bolted in position. Is this necessary ? Surely any slight leak is irrelevant ?

Third point - any advice on the possible pitfalls when remounting pump and then the timing case cover ?

Many thanks,

Mike

Re: Oil Pump on Model 50 - how easy should it bee to turn ?

Posted by paul_standeven at October 12. 2018

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

Re: Oil Pump on Model 50 - how easy should it bee to turn ?

Posted by ian_soady at October 12. 2018

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.

Re: Oil Pump on Model 50 - how easy should it bee to turn ?

Posted by Richard Tool at October 12. 2018

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 .

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

Posted by George Phillips at October 12. 2018

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!

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

Posted by George Phillips at October 12. 2018

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

 

George

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

Posted by George Phillips at October 13. 2018

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

Re: Oil Pump on Model 50 - how easy should it bee to turn ?

Posted by mike_haworth at October 14. 2018

Previously paul_standeven wrote:

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

Many thanks Paul. Many responses. Lots of advice, all taken on board.

Re: Oil Pump on Model 50 - how easy should it bee to turn ?

Posted by mike_haworth at October 14. 2018

Previously ian_soady wrote:

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.

Many thanks Ian. Is this .030" measurement critical ? I left the gap slightly larger when assembling mine on the basis that a little more 'nip' shouldn't harm and that the seal made would be even better. Is that a wrong assumption ?

Re: Oil Pump on Model 50 - how easy should it bee to turn ?

Posted by mike_haworth at October 14. 2018

Previously Richard Tool wrote:

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 .

Many thanks Richard. All re-assembled now. Fingers crossed.

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

Posted by mike_haworth at October 14. 2018

Previously George Phillips wrote:

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

Thanks for comments George. My pump was refurbished by RGM so I know nothing of the internals. I'm going to trust that it has been done properly as I do not wish to pull it apart. All other advice taken on board.

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

Posted by George Phillips at October 14. 2018

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

George

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

Posted by richard_cornish at October 14. 2018

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.

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