10mm bolt on the left side of the diff at the bottom to drain. Big cap on the back takes a 17mm to refill.
If there is water in the diff or the oil is milky best look up some of the threads on diff rebuild.
Riding with the boot ripped is not advisable since water and dirt will enter the swing arm tube and destroy your driveshaft U-joint, also with it sitting on top of the diff input shaft ruin the top seal and pit the shaft..all are bad!
Get a boot, then see if you can pull the swing arm bolt(special tool needed). You can pull the swing arm back far enough to slip the driveshaft off the transmission and slip the new boot on.
I know you may need clarification on what all this involves..just ask, there is more than enough wisdom on the site to draw on.
As far as the electrical goes..yes, new battery may fix electric start, or may not. The headlight is powered by the lighting coil in the engine and battery being NFG won't stop it from working. When the engine is running the light should work, so separate issue.
The electrical is another day and lesson!! Break it down and tackle one at a time is my suggestion.
Last edited by dougspcs; 05-17-2016 at 07:23 AM.
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)