Brake caliper piston size differences. 79 KZ650D2

Hey everyone,

I have a 79 KZ650SR with two 42mm calipers in the front and one 42mm caliper in the rear. Everything seems to be stock. It has has the earlier rotor and caliper style.

Z1 Enterprises only lists a 38mm seal for my bike, and bikebandit and the kawasaki site have different part numbers for the front and rear piston seals, which seems to indicate that they should be different sizes? I measured all the caliper pistons, they are all 42mm. I made the measurement across the whole piston at its widest point. Am I measuring it at the right point? It tapers in where the piston meets the pad.

I am thinking I should just get Z1 Enterprise's rebuild kit for the 42mm for all the calipers, even though the site doesn't list it for my bike because it thinks it has a 38mm. Is this correct? Thanks!

If you don't hear from one of the 650 guys around here, I'd recommend calling Z1E before ordering anything.

I agree. Plenty of time before riding season!

I believe the 38mm is the measurement of the groove that the seal sits in. It's about 2mm deep, so 42mm O.D. -4mm groove = 38mm o-ring for the piston.
Going by memory so could be wrong ,but I'm not taking mine apart to check:woohoo: