AJS & Matchless Owners Club

I am currently restoring a 59 G12, by some accounts the oil supply system is marginal so has anyone got any info on upgrades, one route is to fit later uprated feed and scavenge pumps, but as this model was not fitted with an oil presure release valve, a) would it need one, b) can anyone advise machining required in the base of the oil tunnel to fit a release valve.
is there any info on oiling mods for twins in the club.

Thanks for any advice/info in advance

Andy

Dont worry too much about the reports of marginal oiling you can have too much of a good thing. Ensure that the standard oil pumps are in good condition, try to include a filter, there should already be an oil pressure relief valve at the end of the filter tunnel (I think but will check)

I know little of the G12, so I stand to be shot down regarding the following statements. I read somewhere in a technical document that when the high capacity pump was introduced wider tolerances on the big ends and centre web bearing could be accepted, was this merely a by product, or was the high capacity pump introduced for this purpose, ie. precision = cost. In the same article it was stated that the capacity of the standard pump was far less than is now accepted for modern engines. The relief valve at the end of the filter is to guard against a clogged filter or attempting to pump cold thick oil through the filter, and does not relieve pressure on the pump through out the engine as a whole. Earlier engines had a relief valve fitted in the timing case, at least in the case of the 500 and 600cc. High capacity pumps have a relief valve fitted, on the underside towards the front which passes delivered oil back to the inlet. Fitting a high capacity pump will necessitate a deeper timimg cover.

While we're on the subject of oil systems on the G12 - I am currently restoring a M20 1953. The oil system has me somewhat mystified. The oil is conveyed to the outside of the filter and presumably has to go through the filter to the non return valve. It seems to me that there is nothing to stop the oil bypasing the filter and entering the non return valve. Is the filter just a by pass filter and not a full flow filter? Regards John Powell

John - I have always believed that the oil is pumped to the centre of the filter, if it was'nt the pressure outside the filter would be higher than that on the inside and the 'blow off' valve would never lift.

The oil is pumped to the tunnel surrounding the filter then it passes through the filter and opens the non return valve, then onto the rest of the works. Unlike modern cartridge filters if the the filter does get blocked there is no by-pass and everthing is dumped via the pressure relief valve back to the timing case and then to crankcase for transportaion back to the oil tank. The moral of the story is dont let the filter get blocked or your bike will suffer terminal symptons in rapid quick time.

I see now that the oil is forced through the filter by the close fit of the spring seat in the crankcase tunnel. thanks
John Powell

This is the second time I have been wrong in the last year! Apologies Eric, as soon as I whipped the filter out of the G11 and saw the wire mesh inside the felt I knew you were right. Also apologies to Andrew and John for confusing the issue. Still, it's a good bloke who can admit publicly that he's wrong!