Check the pivot for the foot brake lever..
Remove the cable from the lever and press it down..chances are you will find the pivot is all siezed.
Remove the foot lever and disassemble it..clean the rust and lube it.
This same thing happened to my 250ES.
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)