I've been fighting a dripping drive shaft boot for a year now. The increasingly frequent drip is on the "drive shaft side" of the boot. The transmission side is tight and dry as a bone; there is about a 5-6mm [0.197- 0.236"] gap between the ends of the clamp. It has been suggested that that drip is actually being caused by the rear transmission seal leaking and over-filling the swing arm tube. When I drained my swing arm this afternoon it had 115cc of oil in it; less than spec'd amount. Overfilling is not the problem.
What I discovered, while crawling around on the floor, (yeah I know... grow up, buy a lift) is that the band clamp (on the drive shaft side) is bottomed-out and can exert no further constriction on the boot. I replaced the boot and the two clamps last spring (MAXBMW); the leak began immediately. I still have the old clamps; they are stamped with the number "82" on them near the fitting on the threaded end of the clamp. The new clamps have the number "83" stamped onto them. I do not know if these number correlate to "length", but I suspect that they do. I ran out of time and have not removed the new clamp to compare it to the old.
The only other cause of this leak that I can think of is that the thickness of the rubber on the new boot is less than on the old boot (wouldn't surprise me to discover this) and that as a result the clamp has to be tightened further than before.
If anyone has the time and/or inclination I'd appreciate learning if there is a significant gap (2mm [0.078"] or greater) on the drive shaft side of the back clamp.
Ref. image (not my bike)
Showing "transmission side" band clamp with gap between ends of the clamp.