I’m updating this thread to include a finding on the rear fuel tank mounts (stay).
The 1986 TRX250R stay, RR. Tank part number is 17513-HB9-000.
The 1987-1989 TRX250R stay, RR. Tank part number is 17513-HB9-670.
1986-89 tank mounts all use the same mounting bolts, collars and rubber grommets.
So what’s the difference? The rear stays are a different thickness between the 1986 and 1987-1989. The 1986 rear mounts measure between .125 and .132 in thickness and the 1987-1989 rear mounts measure between .103 and .105 in thickness.
Joe