Leaving away Oil Filter Gasket

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Re: Leaving away Oil Filter Gasket

Postby raffles » Tue Jul 09, 2019 6:41 pm

several twin owners that I know of have made a full crankcase gasket,ruling out any distortion caused by the small
oil chamber gasket. These full crankcase gaskets have to my knowledge been totally successful
Tony

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Re: Leaving away Oil Filter Gasket

Postby GrimJim » Sat Jul 27, 2019 3:32 pm

Hi Yves
I was interested in your description of your oil pump. It sounds like one with a pressure relief valve inserted into the top of the base plate. Do you have a photo? Is it a high or low capacity pump?
You said you had a pressure gauge fitted. What oil pressures do you have on start up and hot. Is the oil pressure constant now that you have unblocked the relief valve?
I hope you don't mind answering these questions as it will help with some problems I have been having with my own oil pump.

Jim

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Re: Leaving away Oil Filter Gasket

Postby dodger » Sat Jul 27, 2019 6:04 pm

High Capacity Pump 2.jpg
One solution to the problem of having no oil pump relief valve is to fit a back plate from a later model.
This has a relief valve built into the body of the pump. You can fit standard pumps to the body or keep the high capacity pumps though you need the bigger timing case as well.
I traced the orifices in the pump to understand better how it worked. From the drawing I made you can see that as the oil pressure increases above the spring tension the HP discharge is relieved back to the suction side of the pump.
I have had this modification fitted to my G9 (1958 600 G11 engine fitted) for a number of years now and leaks have been no problem. I have only the thin paper washer fitted round the filter tunnel and Threebond sealant.

Laurie
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Re: Leaving away Oil Filter Gasket

Postby Yves.Astein » Sat Jul 27, 2019 6:21 pm

Hi Jim,

No I dont mind at all. I am more than Happy to be able to share what I know. Without this forum I would have been lost multiple times.

Here are some Pictures:
Image

Image

Image

Image


Image

There is a thread somewhere here talking about these modified Pumps. Someone used to make them. I have tried to get in contact with him but I believe he is not active anymore.

Some facts I know:
-The pump is not a high Capacity one. Its the early type. (Unfortunately)
- It has metal plates screwed on the outside, which are fitted with a rubber sealing. They seal of the ends of the pump gear shafts. This is against wet sumping. See pictures.
-For the same reason, the gear shafts are also sealed on the other side (towards the cam shafts).
- Then the high pressure valve is fitted. As can be seen on the pictures. Inside there is a metal ball pushed against the overflow oil hole, by a spring.
- The pump was also reworked. Meaning the pump housing was sanded down in order to lower the endplay of the gears. I have an article that describes on how to do this for our pumps. It even provides the desired endplay values. I can share if you like, and if I find it. I have noted down the values from the article in order to not loose them:

Oil Pump :
Teeth to Housing = 0.002“
end Play = 0.003“
shaft play = 0,002“

Oil in Sump after running: 200-300ml

Now to the gauge and the oil pressure:

I have a completely reworked Engine. With freshly grinded crankshaft barings. I am running modern 20-50 oil, with the old felt filter and a modern oil filter in the scavage line.

Before i had freed my pressure relief valve I was seeing up to 100 or more psi when cold.
Now with a self selected spring that fitted into the valve, I am seeing 60psi constantly when cold. Even at idle.

When hot pressure starts to drop down to about 20psi at normal cruising revs. 50km/h 4th gear.

At idle she puts out about 10psi when hot. (I like to have her idle at the lowest revs possible. Because I like to listen to her slowy ticking over)
When comming from a long run on the highway at 37degrees Celsius outside, I could see the pressure to go down even below 10psi. Which has me worried a bit. If any body can sooth my soul there that would be nice.

That pretty much wraps it up I guess.

I would be interested in what kind of problems you are seeing with your pump. Would you mind telling us ?

If you have any more questions, let me know.

Cheers Yves

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Re: Leaving away Oil Filter Gasket

Postby Yves.Astein » Sat Jul 27, 2019 6:29 pm

dodger wrote:
High Capacity Pump 2.jpg
One solution to the problem of having no oil pump relief valve is to fit a back plate from a later model.
This has a relief valve built into the body of the pump. You can fit standard pumps to the body or keep the high capacity pumps though you need the bigger timing case as well.
I traced the orifices in the pump to understand better how it worked. From the drawing I made you can see that as the oil pressure increases above the spring tension the HP discharge is relieved back to the suction side of the pump.
I have had this modification fitted to my G9 (1958 600 G11 engine fitted) for a number of years now and leaks have been no problem. I have only the thin paper washer fitted round the filter tunnel and Threebond sealant.

Laurie


Hey Laurie,

Nice drawing. I was always wondering how the orfices look like inside. One difference with my pressure relief valve though. It spits the oil out at a hole on the side of the Valve when there is to much pressure. The Oil then just runs into the bottom of the Timing housing and from there into the sump. I could see that when I ran the mashine with the timing case open, when trying to find the right spring for the relief valve.

Yves

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Re: Leaving away Oil Filter Gasket

Postby dodger » Sun Jul 28, 2019 7:41 am

Must have been very messy running the engine with the timing cover off.

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Re: Leaving away Oil Filter Gasket

Postby Yves.Astein » Sun Jul 28, 2019 8:38 am

dodger wrote:Must have been very messy running the engine with the timing cover off.


Was ok, I had a bowl underneath. But there was no spray or anything like that. But you could hear her huffing and puffing from the piston airmovement.

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Re: Leaving away Oil Filter Gasket

Postby g80csp11 » Sun Jul 28, 2019 9:05 am

These were modified by Ric Gibbon , unfortunately no longer with us
generally the idea was to prevent excessive cold pressure and minimise leaks from the shafts . he also ground flat the oil pump facing plates at the same time . without fitting new gears you are not going to help pressure . running thicker oil will help a bit . try running SAE50 all year .
I never change the grade for winter / summer use

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Re: Leaving away Oil Filter Gasket

Postby Yves.Astein » Sun Jul 28, 2019 11:43 am

Yes Ric Gibbon that was the Name. Problem is, I couldn’t find any new gears. I was thinking of making new Gears my self. I still have to find out the right gear cutter module. And I have been looking for a high capacity pump, which I could then rework. If anyone has one please PM.

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Re: Leaving away Oil Filter Gasket

Postby GrimJim » Wed Jul 31, 2019 11:03 am

Hi Yves

Thanks for your reply, it provided some interesting information. I had heard of the Ric Gibbon pumps. Thanks for the drawing Laurie, the hole you have shown in the delivery pump discharge port ties in
with the problems I experienced with my pump. I have the latest oil pump with the relief valve in the base, overhauled by Ray Spencer (who has stopped doing this work unfortunately).
I posted a query "Late twin Oil Pump", as when I fitted an oil pressure gauge I was getting 200psi at tick over, although the relief valve had been tested statically at 95 psi. It turned out that the hole
in the discharge port was still tiny, as found in the earlier pumps without the relief valve in the base plate. I drilled out the hole and refitted the pump. I now have 60 psi on start up which remains stable
regardless of revs. I warmed the engine for ten minutes and it remained the same. I haven't been for a run yet as I have a couple of jobs to complete first. I am also using 20w/50 with a later filter in the
tunnel and a canister type in the return line, on a 59 engine. I noticed that the return flow to the tank had been reduced following the mod which would be consistent with the drop in delivery flow due to the
relief valve recirculating oil through the delivery pump. I will check the flow when the engine is fully warm and the relief valve should have closed down to maintain the pressure.

I notice your oil pressure drops off when the engine is up to maximum working temperature. I think this was typical for the lower capacity pumps. There are U tube videos of a twin with an oil pressure gauge
fitted, out for a run - AJS 500 springtwin sunday ride, AJS 500 springtwin 20 1953 part1 and part2. The initial oil pressure is 7 bar (no relief valve?) and drops to 1 bar at idle, around 3 on the road. Lovely
sounding engine. There is also a video from a Mr Sampson of his Matchless Twin Oil Pump Test Rig Mk2 Oct 2016 - very useful.

I have included a photo of my pump. Ray ground the gears, fitted bushes to the delivery pump shafts, fitted a cover which has a spring pushing the gears lightly against the back plate (I haven't looked at that),
fitted a new relief valve and a new bleed valve at for the return pump. All the mods were to reduce wet sumping. He submitted a number of articles to the magazine in the technical article section covering all his
modifications, although I am not sure if they have all been uploaded to the website yet. He didn't modify the return pump apart from adding the new bleed valve he said that was the only thing involved in wet sumping.

Rob Swift posted on the Forum last year that an exchange twin oil pump service would be set up in the new year, maybe you will be able to get some help there.
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