2001 150txrz w/bad cylinder

[oldsalt52]

Is it acceptable to just bore one cylinder over size? Piston galled in #3.
Do the oversize pistons weigh the same as standard. Engine was
recently rebuilt, crosshatch pattern still visible in other cylinders.

[rodbolt17]

yes its acceptable on that engine.
why did a repeat failure occur?

[rodbolt17]

let me add, when I say its acceptable, it means with another piston of whoever made the other 5 pistons.
as you say its been "rebuilt" it may have already been oversized and may or may not have yamaha pistons in it now.
another option would be to have that cylinder sleeved and bored out to match the other 5 holes.
that you should disscuss with a machine shop.