Ive been running a Tony hayward belt drive kit on my "A" for the last 5 years.Prior to that I had one on my Triumph T110 for about 8 yrs. In both cases I Ran them dry.
Its a quality item.
Advantages are ; a) Obviously you get no oil leaks b) no clatter from that area of the bike c) once set you never have to adjust it d) because of the grippy friction plates supplied i find that ,if used with a nylon clutch cable and some of those nice alloy Amal handlebar levers (which have slightly closer pivot centres than the original pressed steel levers) you end up with a clutch that can be operated easily with 2 fingers. I experimented with moving the pivot centres even closer on the handlebar lever which made operation even easier until the lever broke one day because i had removed too much metal.
Tonys uses "Generation 3" belts, Whatever that means (it sounds a bit Star Trek to me) and will run happily in oil if required.
for the grease in the bearing i asked at my local bearing suppliers and they supplied me with a cartridge of sticky blue high temp bearing grease that is supposed to resist being flung off. off course as already stated the bearing is only in use when the lever is pulled in ,I am always aware of this and never sit stationary with the engine running with it in gear.get into neutral as soon as possible and you will never have any trouble. Its good motorcyling practice whatever set-up you are using.
if you ring Mister Hayward up he will happily talk about his product (for hours,you have been warned). Oh, and ask him what the best method of payment is ,you may be pleasantly surprised.
Also, you may be interested to know that he make and supplies the dynamo belt drive kits for SRM (or he did when i bought mine) and so you can buy them from him without the mark-up that SRM put on them.
if using a nylon clutch cable I was advised (by the manufaturers )never to use oil or WD40. use "Duck oil" or apparently the cablw ill get gummed up and become difficult tp operate
Mike