A comment if I may concerning sealing the dynamo against the back of the sprocket housing. Oil loss from here is usually due to excess oil in the primary chaincase. It's well known that most Twins have a tendancy for oil to pass through the drive-side main bearings necessitating the need to drain off the surplus via the level screw.If you seal the dynamo in the way some have described you will prevent the primary chaincase from breathing so any pressure build up will be forced into the dynamo. (Or into the gearbox, won't it Hugo Myatt?!) The felt ring in a Miller dyno won't stop much, far better to use sealed armature bearings which are readily available from bearing stockists.
I can confirm lens statement to breathing through the dynamo.
I fit the E3L to my D, line up and secure. I then remove the drive sprocket and drive boss (keyed to the armature shaft) and seal the dynamo to primary mating surface from the inside with silicon. (I’ve tried the bead of silicon on the mating surfaces trick a couple of times, but I end up with silicon everywhere and it still leaks afterwards!!)
The last time I inspected the dynamo, it looked as though it had laid on the sea bed for 10 years! Inside was full of rust, and the bandage wrapping the coil had almost totally disintegrated.
The primary is definitely breathing through the dynamo, and although I have no problems with oil in the dynamo, the air being transported is carrying a lot of condensation (I’ve ridden 200 miles in winter before now, and on looking into the primary to adjust the chain, have found the oil to be milky brown (emulsion?), so condensation is a definitely problem.
Theoretically, if you could seal the primary effectively (dynamo, gearbox cover plate & detent housing, kick-start shaft tunnel etc) then the pressure in the primary would stay constant.
If no more gasses are travelling through the bearings, no more oil would be transported through the bearings and your primary oil level would stay relatively constant.
These are all unfortunately answers to the symptoms and not a solution for the cause.
This would be primary mainshaft seal or sealed bearing.
I’m looking at fitting a sealed bearing at the moment, but have yet to find a way of removing it from the mainshaft/housing without splitting the cases.
Anybody managed this before?