Oil pump plunger drive from crank.

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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NaughtyNetley
Posts: 85
Joined: Fri Dec 28, 2018 12:09 pm
Location: Cornwall

Oil pump plunger drive from crank.

Post by NaughtyNetley »

IMG_20190321_190120.jpg
Hi, just got my first British motorcycle, a 1959 ex AFS G3.
I was told there were oil feed troubles so no surprises.
I have discovered the "screw" that drives the oil pump plunger is buggered as is the plunger. Is the "screw" part of the crank assembly available separately or will I need a whole new crank?
A friend has a couple of old cranks so I have plenty of available spares.
Any advice gratefully accepted.
Neil
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SPRIDDLER
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Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Oil pump plunger drive from crank.

Post by SPRIDDLER »

Yes, the oil pump drive scroll is an integral part of the timing side axle which must be replaced as one.
NaughtyNetley wrote: A friend has a couple of old cranks so I have plenty of available spares.
If you are choosing one of a friend's axles be aware that there are 'one start' and later 'two start' scrolls (axles) and matching (one and/or two start) oil pump plungers. One start and two start scrolls (axles) and plungers are not interchangeable. Look at the end of the plunger which on yours (1959) should be marked '2S' to identify it as a two start plunger.
You will of course check the inside of the pump housing, plunger guide pin, timing side bush, all bearings and filters and oilways in case of residue or damage from the distributed bits of the scroll.
Do you have any history of previous problems or work done on the engine? As a pure guess I would suspect that the damage to the scroll could possiby be the result of a previously mismatched scroll and pump plunger.
If you don't have them you can find original manuals etc. under 'Books' here:
http://archives.jampot.dk/
To replace the axle you will have to split the flywheels and crank pin (a press is required) and reassemble/realign the flywheels, also using a press, with great accuracy (within one thou run-out).
(Apologies if you are familiar with these points).
This is a very worthwhile practical read:
http://archives.jampot.dk/technical/Spe ... hanics.pdf
Splitting and reassembling the flywheels/crankpin is covered here:
http://archives.jampot.dk/technical/Gen ... ctions.pdf
'There is a tide in the affairs of men
Which taken at the flood............'
NaughtyNetley
Posts: 85
Joined: Fri Dec 28, 2018 12:09 pm
Location: Cornwall

Re: Oil pump plunger drive from crank.

Post by NaughtyNetley »

Thank you Spriddler, most informative.
As I mentioned, I am new to older motorcycles though I have a good friend with much knowledge who is advising what other things will need attention whilst the engine is apart but I'm always happy to receive additional input.
Thanks.
Neil
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