Thanks Lane, Arsey30,

I do have a spare master cylinder. Have not serviced the one on the bike or the spare one though.
If lowering the fluid level doesn't improve, I'll have a go at replacing the master cylinder. Wish the bike was at my place, it's sitting at the mechanic's atm, and I'm struggling to find the time to go there!

That reminds me, gotta post some pictures & videos in my member's introduction!
https://docs.google.com/leaf?id=0B-bAuD ... y&hl=en_US

https://docs.google.com/leaf?id=0B-bAuD ... k&hl=en_US

http://www.youtube.com/user/TheMyagui

Oh damn ... just one more trackday around my parts this year ... Please be sunny, please be sunny!

andrelopes wrote:
Calipers were refurbed and pistons move smoothly, fluid replaced and obsessively bleed, no improvement.

Did they use the correct seals for the pistons?
The seal for the piston is actually what is responsible for pulling the pistons & pads off the disc.

The seal should have a square lip on it.
When you apply the brakes, the pistons moves toward the pad and slightly distorts the seal.
When you release the brakes, the seal retrns to it's original shape, and with it brings the piston back.



A circular O-ring will not have the same effect.

Best way to tell if your MC is holding the pressure and not your Piston seals, is to take it for a hard ride, then when you pull over, quickly open one of the bleeder nipples on the caliper.

If it spits a little bit of fluid (rather than dribbles) you know your MC is stuck.

Rebuild the spare master with new piston & seals, use an OE reservoir and for to start also an OE lever. This will sort it.

Brakes are a simple system, if you have already eliminated the calipers then it can only really be the master, eh?