The '85s don't have a very good weather seal, the '86s is better but not perfect.
It has to be the way you are closing them up after your brake work..got to get them as water tight as possible. Lots of grease on the rubber seal around the drum lip!!
In the fall I pull the wheels off mine, spray the crap out of them with brake cleaner and seal them up so they won't sit thru the winter months with any dirt or moisture..
The problem with your ATV brakes is they aren't working regularly enough to get hot and dry them out..any moisture stuck inside riding is sure to rot the shoes off!!
Also, get some OEM shoes!!
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)