Oil Bath Primary - Sealing your Primary Oiler
It's easy to isolate the primary, you can do it when the bike is assembled, but a cleaner job can be done by taking parts off, you need to pull the inner primary to permanently plug the connections off with pipe plugs, but you can get by with just cutting the hoses and inserting a bolt into the hose to plug them off for quite some time until you can "do it right" at the next major teardown).
First I'll explain the hoses coming from the primary and what you need to do to seal it off. There is a 3/8" vent line coming from the middle of the inner primary that "tee's" into the vent line going from the motor case to the oil tank. There is another 3/8" oil return that connects to the rear of the inner primary, near the inside bottom surface...it goes from the inner primary back to the motor case, where it connects to a fitting just inboard of the oil pump (near the crankcase vent fitting). And finally, there is a small 1/4" line connected to the top of the oil pump that supplies oil to the inner primary, through a small fitting in the middle of the inner.
You need to remove the vent line from the inner and plug it off. You will no longer need that "tee" in the motor case to oil tank vent line, you can replace it with a single length of hose. You will need to remove the oil return line from the rear of the primary to the motor case and plug both ends (as stated before, you can simply cut the hose and shove a bolt in each end, securing it with a hoseclamp...this works, but I prefer to use brass plumbing plugs, 1/8" pipe thread, to close everything off. Then, disconnect the smaller oil supply hose at the oil pump. Leave the hose connected to the inner primary fitting. Run the hose down under the frame, so it can act as a vent for the inner primary. If ya' don't vent the primary to atmosphere, as the lube inside warms up the primary will pressurize and oil may seep out of the gaskets. Again, you can plug the nipple at the oil pump by simply leaving a short section of hose on it and plugging it with a screw or you can pull the little nipple out of the oil pump cover by twisting it back and forth with a pair of pliers, then tap the hole for a small machine screw and screw it shut. As I said, while the plugged hose method works, I really hate the look of short hoses plugged with something and it's not much more work to do it the right way.
Once you have the oiling system disconnected, you need to add oil to the primary. I run straight 30 weight auto oil. Never had a problem with clutches, but make sure you are running a wet/dry clutch...a plain "dry" clutch will act up. As far as oil, it only takes about 1/2 quart or so. Just have somebody set on the bike in an upright position, pour the oil in through the derby cover until it just touches the bottom of the clutch shell and you're set. You don't need to have the chain in the oil, it only needs to be enough oil so it contacts the bottom of the clutch shell...as the clutch shell spins, it'll sling the oil around and lube the chain no problem, guaranteed.