[Greybeard]

That makes sense, Vic, thanks.
That'll give me a nice little project to get on with whilst the 2 pack is hardening on the chaincases 

Steve

[VicYouel]

Took a look at Eric's bike today..... it has an enclosed rear chainguard so could not see what goes on in the primary chaincase and bihnd but there is a screw and nut on the primary outer that to all intents and purposes is almost definitely an adjuster to set the oil drip flow to  the rear chain enclosure.

forgot to take my camera!

Vic

[Greybeard]

Thanks, Vic. That is appreciated. Having just re-read what I've written, i realise now it can't be a breather as there is any amount of fresh air around the clutch shaft  It must be an oil feed for the chain.

Steve

[VicYouel]

Steve,

Eric Patterson who runs our local jumbles at Kempton has just acquired a 1937 model 9 600cc ohv which looks to all intents and purposes like your machine.

I'll try and get a look at it to figure out his breather when I get the opportunity.

Vic

[Greybeard]

Whilst I'm waiting for the new gearbox parts and my engine sprocket to turn up I've begun stripping/priming the chaincases ready for respraying to a suitable Sunbeamland standard  I notice that at the very back end of the casing is a threaded 3/8th hole that has obviously had a bolt of some sort in it in days gone by. It's also threaded BSC - I note that Sunbeam used Whitworth and BSF too all on the same component - I'm sure they had their reasons 
Inside the cases above this hole is a small scoop with a drilling from the outer chaincase through to the thread. I'm guessing that this was some sort of drip oilfeed to lubricate the rear chain. I imagine that it was something along the lines of a banjo type bolt with a cross drilling into a waisted section adjacen to the case's hole leading to longitudinal hole to allow oil from the primary case to drip out onto the drive chain. Before I set to and make one, can anyone confirm that this is what it is and also whether the diameter of the drilling is important? I don't want to be leaving an oil slick behind 

Thanks. Steve