There is a mod out there that you can replace the front brake back plate from a YZ to 1984 Yamaha TY 250 Mono as the existing has just seized up and split its a fault with the front brake and they grab when they become wet.

Not sure which model YZ there are a few on ebay USA but need to know which one, so if someone had one they could measure, its a different configuration with the brake actuating arm on the outside and not internal one like the TY 250 mono the overall dimension the brake linings the drum is 134mm internal diameter 5.1".

You can get one from the UK 110.00 GBP = 233.645 NZD then there's the shipping!