Z1OwnersClub GB

I have finally got the master cuylinder disassembled (very gunked up piston) ready for a repair kit. I can't get the relief port cleared and resisting putting a fine drill bit into it as not sure what diameter the final hole is - looks tiny on the schematic drawing in the workshop manual - any advice appreciated.

pull a strand of wire out of a wire brush to clean the hole do not use a drill

It took a while and several bent/broken wire strands but eventually got it cleared. Many thanks z1bman as this worked much better than the soft fuse wire I had been stuffing around with.