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Re: M20 oil pump

Bit late now but all BSA oil pumps are made of rubbish metal. Always store them in a container of engine oil, otherwise they dry and warp.

Re: M20 oil pump

Ian Clare
Bit late now but all BSA oil pumps are made of rubbish metal. Always store them in a container of engine oil, otherwise they dry and warp.
Really,
Rubbish metal ?
BSA knew nothing about the metallurgy of the alloy they used to make about 3,000,000 oil pumps most of which have outlived their design life 4 times over.

Zinc is an excellent material for a precision casting, but like anything made by man, it has a finite service life.

email (option): bsansw1@tpg.com.au

Re: M20 oil pump

Most of the 3,000000 oil pumps you talk of spent most if not all their working life in oil.

Re: M20 oil pump

The die castings of the pump body and end plate deteriorate with age and the result is localised expansion of the material as it corrodes...This leads to reduced internal clearances and a 'tight' pump as the gears are pinched by the body material.

Lapping or very careful machining of the pump body, holes for the gear spindles and end plate can bring the pumps back from the dead...However, care should be taken not to produce excessive clearances or an increased tendency to wet sump will be the result...

Corrosion may be increased by prolonged exposure to the atmosphere but pumps fitted to engines or pumps kept submerged in oil can also suffer... In fact I wouldn't mind a fiver for every M or B Series engine I've stripped that had a tight pump...Most do...

As noted by Trevor, the intended service life of these pumps has been far exceeded and it is that causing the problem, not an issue with the material originally specified ...Ian

email (option): ian@wright52.plus.com

Re: M20 oil pump

Is it possible to machine one out of steel?

email (option): michasteinmann@gmail.com

Re: M20 oil pump

i have used original very good -
if u interested i can sent photo

email (option): sl_hussein@yahoo.com

Re: M20 oil pump

Norton pumps from the 1930s were monkey-metal too, although they don't seem to suffer from the same degree of problems as BSA...probably because the internal tolerances were more tolerant...Later twin cylinder pumps were steel-bodied and Andover Norton now make steel versions of the opposite-handed singles pumps.

The best option would be for a decent engineering company to be offering modern steel versions of the M20 pump but all the time there are enough older pumps working, it is unlikely to happen.

Re: M20 oil pump

Draganfly used to sell a pump made from high grade steel but I can't see them on their site anymore, although they do sell the individual parts and offer a complete exchange reconditioning service. The 13 tooth gears were changed in 1955 to higher output 12 tooth gears which are interchangeable in complete sets. Ron

email (option): ronpier@talk21.com

Re: M20 oil pump

Michael
Is it possible to machine one out of steel?
It is possible to do anything.
Any one with a £ 4,000,000 auto scan & 3 axis machine could whip one up in about 20 minutes.
But they generally charge out around $ 300 / hr for using it + set up fee & with 2 hr minimum charge out

If they are the massive problem you seem to thing they are and considering the vast number of B & M series bikes out there that used them then there would be 1/2 dozen aftermarket parts suppliers getting them made up by the truckload.

And further to what Ian said, early ones were lower copper and what they actually do is creep over time, similar to lead sheet or plate glass. Highish temperature accelerate this and yes some will need a bit of relief.

It is simply a matter of price.
A cast iron pump would cost near 10 times as much to make as one cast from a Mazac ( registered trade name ) type of alloy.
Unfortunately motorcycling journalist could neither pronounce nor spell Mazac so they termed it "monkey metal" or "pot metal" and then inferred that every problem ever suffered by any motorcycle in the entire history of motorcycling was due to the use of these alloys , where as they should have been printing " the use of a Mazac cast pump body has further reduced the price £ 5.00 and trimmed 1/4 lb off the dry weight"

Motorcycles would last a lot longer if the crank case was made from cast iron as well or perhaps cast steel then machined all over.
That would be great and of course con rods should only be made from nickel alloyed with vanadium & titanium and of course a bronze head. will never wear out.

A reasonable machinist could probably run up a case machined from a lump of 4140 in about a full day for a one of.
So that would run around the £ 400 to £ 600 if done by a jobbing engineering workshop.
Then you will need to decide if you want a bush in there or were happy with steel running on steel.
After that you would need to look as sealing against the alloy case allowing for differential expansion between iron / steel & the 7% silicon sand cast alloy crankcase.

Now being a BSA owner I will happily buy 5 of them from you @ £ 30 each cause I can get a good used one for £ 40.

email (option): bsansw1@tpg.com.au

Re: M20 oil pump

SRM do the A10 pump complete for about £300 plus vat....ABSAF in Holland do a Gold Star pump for about £400 plus vat...That includes a new sump plate, lengthened plate studs, lengthened pump mounting bolts, gaskets and the pump itself...

The reason for that is that the pump has a higher capacity and is a little taller than the standard unit...

The Goldie pump will fit other models but might be classed as a bit exotic for an M20!....and there might be issues with clearance for the sump guard... That gives an idea of what new pumps might cost if they were made available, though of course, a body only would be substantially cheaper....

Most machine shops with a CNC machining centre could turn out the pump body without any real difficulty and steel or bronze would be a suitable material choice....

All it needs is a willing volunteer to get the project rolling...:laughing: .....Ian

email (option): ian@wright52.plus.com

Re: M20 oil pump

Hi All,

Some 10 years ago, there was someone who sold new CNC machined BSA oil pump body on eBay.
They it was made really well and of a good grade aluminum. (You would get the body only)

It was not expensive, as far as I remember, but was not there for long.

Below are few photos of the high capacity ABSAF pump set
(The higher one, and with the new filter, sump cover and screws) and the exact copy
of the original, made of aluminum. (Smaller)

Alaso, at the past there was an option to send your oil pump to "Draganfly" and receive a new made pump back.
I am not sure if this service is still available.

Noam.





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