Questions? Looking for parts? Parts for sale? or just for a chat,

The WD Motorcycle forum

WD Motorcycle forum
Start a New Topic 
Author
Comment
Oil pump tightness

This has probably been asked before, but I'm sure it bears repeating. How tight should an M20 oil pump be? I've got one here (actually from my B33 engine), that I can't turn with my fingers, but can turn fairly easily with a pair of pliers. The pump has been lying around for a while, incidentally, and probably needs cleaning. But should these be loose enough to turn easily in the fingers?

I can't see any distortion in the pump body, and I can't see any cracks or other damge. Can anyone enlighten me?

Also, are these (B33) pumps interchangeable with M20 pumps? Or is there a different flow rate or some other difference that isn't immediately apparent? Thanks.

email (option): dannydefazio@sumpmagazine.com

Re: Oil pump tightness

Hi Danny,
This has been covered before in this forum.

Summarised to the best of my knowledge and memory,

Apart from a post war change to the number of teeth of the actual pumping gears, the pumps are identical from 1937 to 1962-3.
The change was done to make the gears cheaper to manufacture, a spinoff was that it very slightly increased the oil delivery.
The insignificance of the differences in flow rates renders any pump suitable for any engine.

Pumps should turn with fingers.
No obvious cracks or distortion is a good sign.
You seem perhaps reluctant to dismantle it?
If so, you could try soaking it in lacquer thinner or similar for a few days (to un-gum it)and cross your fingers.

If that shows no improvement.

Immediately submerge the complete pump in oil, while you think about your next step.

You can possibly mount a spare pump drive in a drill press and "run-in" the pump (you must maintain at least a partial oil supply to both scavenge and feed gear sets, or pump may weld itself together)

Or dismantle and determine where the tightness is occurring, probably in your case in the shaft bores of the main body, due to the initial onset of stage 1 body death by explosive corrosion.

Carefully ream the shaft bores as required, in your case half a thou will probably show a vast improvement.
Do not ream to excess or you will create a chronic "wet-sumper".

Always store spare pumps and bodies submerged in oil, even NOS and grungy old ones.

"first, do no harm"

Neale

email (option): n.gentner@bigpond.com

Re: Oil pump tightness

Hello Neale, thanks for that. I did say in my post that I thought this had been covered. But you can't follow every thread all the time - and you could grow old trying to work through everything that's already been talked about.

I'm not at all reluctant to dismantle the pump. I just wondered about the tightness. That's all. I'll try your suggestion about soaking it. This pump, unfortunately, hasn't been stored in oil (it came with a dismantled B33 engine and was wrapped in a cloth; I didn't even remember that it was there). But with luck, it's recoverable.

Thanks again for the tips.

email (option): dannydefazio@sumpmagazine.com

Re: Oil pump tightness

Hi again Danny

The entire forum is easily searchable using the box beneath the picture.

Cheers

Neale

email (option): n.gentner@bigpond.com

Re: Oil pump tightness

Thanks Neale. I did search the posts and found what I needed.

email (option): dannydefazio@sump-publishing.co.uk

Re: Oil pump tightness

Hi Danny - I have a similar siuation, my pump turns easy on the end of a small spanner, but quite stiff if trying to turn with my fingers. I've had it apart, looks very clean inside, put back together (but not too tight) this seemed to improve the sutuation, but not much.

It seems that the gears press hard against the inside of the housing to form a seal of some kind, so there is bound to be at least some friction experienced.

Anyway, it pumps oil perfectly well and no corrosion or warping is present - so i'm just going to fit it and hope for the best!

Andy

email (option): adh325@hotmail.com

Re: Oil pump tightness

Thanks, Andy.

email (option): dannydefazio@sump-publishing.co.uk

Re: Oil pump tightness

On the B31 engine I am building the oil pump was tight enough to need a small spanner to turn it.
At work we have air compressors that as the lobes get dirty reguire more power to drive them until they burn the motors out. It is amazing just how small a coating of dust stiffens them up.
I took my pump apart, and although the gears look fairly clean there is very thin coating on them between the teeth--almost looked like a varnish (a powerfull magnifing glass was needed to see it). I took them apart and soaked everything in brake cleaning fluid ( stuff for cleaning dirty slave cylinders/pistons on bikes and cars).
Then gently scraped the worst of it off the gears, then got them shiney by wiping them with a rag and thourghly cleaned the pump body.
The gears have to be as near spottless as you can get them.
As you reassemble you can turn each individual pair off gears to see that they are clean and rotate freely.
The tightnes does not come from the gears rubbing the pump body, but from that varnish skewing the gears until they bind in their drive.
Now I can turn the drive with my fingers.
Dont forget to fill it with oil to stop any corrosion of the alloy body

email (option): gasboy@btinternet .com

Nieuwe pagina 1