The book says only grease is needed, I used Wellseal.
Also check that there are no digs where the cases join just in case the joint face is not  quite flat.

John Hood

Both ball valves are necessary to give good oil pressure, without the top one the telltale will not operate fully.
The reason for your over oiling at the rocker box may be the same as my 9A when i first got it on the road, I had oil dripping off the bottom of the engine it was so bad.
At the rear of the bottom gallery in the rockerbox, the one with the plug with the screwdriver slot, should be one or two felt seals to control the amount of oil getting to the valve guides. Because the screw at the front of this gallery has a hole in the middle a pool of oil builds up in the gallery and the felt seals just allow a gentle weep of oil to the guides, or at least should, they do on mine.
I made two felt seals about 5mm thick to do the job, Try just one to start with which is what I did.
Good luck  ..John hood

I applied an 0.5mm paper gasket and it was fine. However, I still have a tiny amount of oil at the joint. Maybe an additional thin layer of Hylomar on both gasket sides helps.

Gents

A small amount of oil was leaking between the base of the barrel and the top of the crankcase on my 1932 Model 9. Not much, but annoying nevertheless. Removing the barrel revealed a paper gasket? smeared with some sort of sealant. Not great - see attached pics.

Does the club have a spare gasket I can purchase?

Otherwise, I guess I'll have to make one. Would 1/2mm Flexoid do a better job or does it need to be paper thin?

Hello Sunbeam colleagues
Concerns oil system of my Model 9 (1936).
Can anyone inform me what is the purpose of the overflow valve at the rocker box.
Please see attached diagram.
I am currently trying to control the oil leakage from the rocker box at the rocker arm bearing. I have renewed the bearings with minimal clearance. Reduction of the orifice is not possible because this would also compromise the oil supply to the camshaft distribution. I am now doing a test by feeding a small oil flow for the orifice to the pushrod area via a newly turned oil supply fitting and a newly drilled oil channel. During a test with an oil syringe, this appears to work well. I reduced the orifice to 0.5mm. Whether it works in practice we will find out.

Thank you Paul, is it worth refering to 1st gear engagement to mount the clutch stop ?    regards, Thomas

Have a look at:https://marston-sunbeam.org/sunbeam_shop17/index.php?id_category=7&controller=category. We can supply good quality copies of all 1935 Marston manuals, instructions, spares list and catalogues. Although not workshop manuals in the modern sense, these booklets will be very helpful in maintaining your machine. Although not illustrated, the spares list gives you a good idea of what should be on your Lion, and the illustrated 1932-34 list shows what they should look like.

P.

Have you tried F.W.Thornton in Shrewsbury?

Hi everyone,

Would anyone have a spare 7.5:1 piston for a 1930 machine they would be willing to part with? My cylinder is +30 thou so I can take the bore out if necessary.

Thanks
Michael Thearle

https://cyclesautomoto.files.wordpress.com/2011/07/1927-amac-catalogue.pdf
Some similar non needle pictures and parts lists at the end of this manual.