AJS & Matchless Owners Club

Two questions about the engine oil filter ( behind the plug with the screw head in it, under the generator, drive side). On investigation I have no felt filter in there.
- is it a 'modification' to leave it out- deemed unnecessary?
- is there a diagram of what should go in there in what order, I can't work it out from the spares list?

assuming the chamber is totally empty of everything you'll need the following and this is the sequence for installation.
1. 018120 steel end cap for filter
2. 014235 filter
3. 014240 ali filter end cap
4. 014241 spring for pressure reflief
5 016179 this is the end cap you unscrewed which has the relief valve in it, make sure you have 011642 fibre washer fitted.

Thanks, that's extremely helpful- I'll hunt down those parts.

I wonder if it has been left out due to a modification carried out by a previous owner? My 58 G11CS as manufactured had no timing side oil pressure relief valve. It would chuck oil out from behind the Dynamo on start up with the oil cold. On splitting the cases there was no paper gasket round the filter housing and this was fitted. However with the cases apart the engineering brains in our section recommended fitting a relief valve. We decided to fit the later type as it does not fall out when the timing side case is taken off BUT it required the fitting of the later type of filter which is attached to the filter cap or the valve is pushed open by the earlier type filter.
So if a similar mod had been done to your bike but the later type unit filter was not available the filter as described by Rob may have intentionally been left out. (Sorry the earlier parts are not available as they have already been sold to another club member!)

Thanks for the idea. I had a look at the parts list and notice the with the later bikes the cap (which screws into the crankcase) doesn't have the ball and spring inside. I had a look at my cap and it is still fitted with these and I'm guessing if the later relief valve was fitted you would take these parts out, so it's mostly likely the older type.

Actually lets call it by it's proper name and function, it's actually a non return valve that captivates the oil to the rockers ensuring they don't run dry on start up. The early 2 valves were serviceable as indicated by the removable screw along with spring and ball. The later ones had this arrangement captivated by a ring staked in from the inside and it can't be easily serviced. Both are interchangeable as a whole unit with out the need to swap out parts.

ajscomboman wrote: ↑Mon Jan 17, 2022 9:41 am Actually lets call it by it's proper name and function, it's actually a non return valve that captivates the oil to the rockers ensuring they don't run dry on start up. The early 2 valves were serviceable as indicated by the removable screw along with spring and ball. The later ones had this arrangement captivated by a ring staked in from the inside and it can't be easily serviced. Both are interchangeable as a whole unit with out the need to swap out parts.

The oil in the galleries up to the rockers quickly drains down to the sump through the crankshaft centre bearing when the engine is not running, so the 'non-return valve' does not help in that matter. Its main function is to retain the oil in the oil filter tunnel, so the oil delivery to the centre bearing, connecting rod bearings, and rockers is not unduly delayed upon startup.

Well I am not sure I fully understand the oiling system on a 58 twin and stand to be corrected by those who know much more. However my understanding of the sprung ball is that it is not a pressure relief device but it is an anti-drain device to keep oil from draining back from the cams and rockers when the engine is stopped. Indeed the 1958 parts list specifies the end cap you describe, 023331, as “Cap assembled, oil filter housing, (also accommodates oil non-return valve)”.
Now the filter assembly itself does have a spring part number 014241 which presses on the ali end cap 014240. This would act as a relief valve but only to allow oil to bypass the filter if it is too blocked. If it vents it would do so into the filter chamber. On the 58 models at least this is a chamber without a pressure relief into the primary side which the earlier and later bikes have albeit of different designs. So there is no relief if the pressure builds up until the oil heats up and thins, hence the risk of leaks at the crankcase joint.
Up to 56 there is an “oil relief valve (Located in the timing side crankcase close to the oil feed pump)” part 016524 and spring 016522. This one falls out when you take the Timing side cover off. From 56 to 59 no oil pressure relief valve seems to have been fitted.
From 1960 an oil pressure relief valve is reintroduced, this time located in the timing side crankcase half and it does not fall out when you take the timing side cover off. Parts are 026133 piston, 026132 spring, 026134 washer, 040049 circlip. With this fitted you need a different, shorter, oil filter to avoid it actuating the relief valve. The filter is one piece 026139 and it is “assembled” with the endcap and filter all one piece. The illustration in the parts list clearly shows that in addition it still has the oil non-return valve fitted.
My point was that if anyone had trouble with oil leaks from behind the dynamo they may have retrofitted the oil pressure relief valve which is missing from the 58 model and if they did they would probably do as I did and opt for the type that does not fall out when you take the timing cover off. If they did and if none of the unit "cap and filters" were available they may have chosen to leave the filter out.
Try shining a torch down your filter tunnel and see if anything is projecting into it at the far end, if it is then whip off the timing cover and see if a later type relief valve has been fitted. Trefor It is also helpful to include the year of your bike, as you can see from the above, either in your post or in your personal details.

clive wrote: ↑Mon Jan 17, 2022 11:37 am Well I am not sure I fully understand the oiling system on a 58 twin and stand to be corrected by those who know much more. However my understanding of the sprung ball is that it is not a pressure relief device but it is an anti-drain device to keep oil from draining back from the cams and rockers when the engine is stopped. .......

The oil from the rocker galleries is quickly drained down to the sump via the centre bearing, so the 'non return valve' has no function in that respect. That is obvious when looking at the schematics of the twin engine. Look at the red arrow - the feed to the centre bearing goes down there, and it is AFTER the 'non-return valve', therefore this valve cannot stop the oil from draining via the centre bearing. The function of the valve is to (try to) hold the oil inside the filter cavity.
.

ok but it still is not a pressure relief valve....