Congrats on the SN! 701 engine or 650? pics?
Things I do every couple rides are:
-lube steering cable, at the steer nozzle and the turn plate near the bars
-lube thottle cable
-spray down engine and carb with fresh water after every ride, then I use Yamashield spray over anything metal. You can use wd-40, I just happen to have a few cans of Yamashield.
-Inspect for loose bolts, broken motor mounts, cracked fuel lines, etc.
-I flush engine with fresh water every ride because I ride salt water. I would reccommend getting a flush kit if you plan on riding salt water.
There is on some SN's a grease zerk for the midshaft housing, but if yours is a stock 91 I dont think it has the zerk, my 93 doesn't. If you do, the grease is not really for the bearing, its to keep water out. Just a few pumps and your good. You dont want to blow the seals out.
When I winterize I fill my fuel tank with fuel, then add the correct amount of stabil. Run it and flush it out with fresh water(because I ride in salt water almost 100% of the time). Then fog the cylinders with fogging oil.
Some of this might not be as necessary if you ride fresh water, but thats what I do.