[Rick Parkington]

Hi Norrie,
Wheel bearing wise, I found that BSA C11 or C12 half width hub cups were similar...but not quite right and I couldn't find anything else. Certainly Chris Odling 01853 300191 (on Seil over the Atlantic fae Oban) machines the hubs to take ball-races which is probably the best option, enabling an easy change in future.
As to the tap I can only guess that the leaks were so bad that a previous owner arranged a roadside top-up system; I can't see any other reason. Although as Paul says there's no seal between gearbox and chaincase, there should be a scrolled washer that tends to 'screw' oil back into the box and it certainly shouldn't be 'total loss'. My '28 Model 9 has a level plug which I don't think is original - it may be a later box - but height wise, if you look at the six studs/nuts that retain the cover (R/H side) the plug is just below a line drawn between the middle two.
I find the worst leak source to  be the gearchange lever which sits below the oil level. It is sealed by a cork washer inside a large hexagon gland nut. Unfortunately changing the washer requires a complete gearbox strip. i have heard of people replacing the washer with an O ring but inmy opinion that isn't the right thing to use, the gland nut is there to compress the seal which won't work properly with an O ring; cork or tallowed felt is the answer but it's a palaver to change.
Fluid grease is good but easier to fill with the outer cover removed - you'll be there forever trying to get it into the filler neck and I would always prefer to use a bit of oil with it anyway to get into the obscure bits - like up the sleeve gear bush. Grease causes a lot of drag too which may or may not matter. I remember thinking I was being clever once by filling my leaky '32 4 speed gearbox with (SAE 140!) Castrol D but when I went to turn the rear wheel on the stand I couldn't believe how stiff it had become in neutral, reckoning I'd have lost about 5mph top speed I drained it out and put more effort into sealing the leak!
Cheers Rick   

[phutton]

On these early models, there was no oil seal between the mainshaft and the primary chaincase, so you could never a gearbox full of oil. A lot of people use semi-fluid grease, such as Penrite, and push in about 1/2lb of the stuff. The occasional pumpful via the tap just keeps it sweet!

No idea what the second tap is for - owner-fitted?

P.

[VicYouel]

Sorry but I am not able to comment on your gearbox oiling question(s) as I lack experience and knowledge.  Chris Odling has supplied sketches to me in the past to show how to adapt wheel bearings to modern bearing races..... and of course could no doubt do the work for you.

[Norrie]

Hello All from Scottish new Model 4 owner 
Having had the front wheel off on my recently acquired 1926 Model 4 the bearing cups fixed in the hub are badly pitted and need replacing. Are these cups available? or do current riders/custodians replace with modern sealed bearings and if so what other parts are required in the hub to allow fitment?
This smart looking machine, which was restored overseas, also has a tap in the oil pipe to the gearbox which I haven't seen elsewhere. It looks like it allows oil, other than from the tank via the two way tap, to be fed into the gearbox. See attached.
Changing the oils before trying to start the machine I drained approximately 300mls of oil from the engine but nothing came out from the gearbox. I have heard it should be full of grease or that I should use chain saw oil. The 'Instruction Sheet for Side-valve Sunbeams' sheet I got with the machine tells me that the gearbox requires a pumpful of oil (same oil as engine) about every two or three hundred miles. Is this enough lubrication for a gearbox? Every other motorcycle I have owned the gearbox internals have been pretty well submerged in oil.
Apologises for the beginner questions but I am keen to learn as much as possible before using the machine.
Best wishes
Norrie