Dunstall Front Brake Master Cylinder (size?)

HI,

I have exhausted my web search abilities (including this forum)- I'm on the hunt for the piston dimension of the front brake master cylinder. I'm currently running the dual front disc Dunstalls on what came with the bike (D2 brakes- I think they are originally from a kawasaki) which I cant seem to find the piston size for either. My goal is to replace this master cylinder with a Brembo equivalent (the D2 seems to be leaking some fluid from the reservoir and does not match { I know the horror! } my new Brembo hydraulic clutch from CNW)

I tried to hunt the size on dunstall website, other forums and nothing- anyone who is a dunstall freak or kawazaki guru - please help. I would hate to take the master cylinder apart JUST to measure the piston. Thanks !

video of the bike: http://youtu.be/vNb4mBmZtz4

recently got tank painted to match the rest of the bike

Rather than trying to match the original Dunstall master (which probably wasn't that good to begin with), use the chart from Vintage Brake (http://www.vintagebrake.com/mastercylinder.htm). I don't have my Dunstall setup any more, but if memory serves me well, the pistons are 1.5 inch (38 mm) and there are 4, so a 15 mm piston mastercylinder will give a ratio of 25.67 while a 14 mm master gives 29.47. Vintage Brake likes a ratio of 27 to 23:1, so a 14 mm may be too spongy while a 15 mm will be on the wooden side.

Thanks Ron - I knew someone would look at the problem from a different angle ! Cheers !

http://www.nortonownersclub.org/noc-cha ... /930118144

....light alloy fork sliders with integral caliper housings (including the 1-1/2" diameter pistons and friction pads)....

Click to expand...

The master cylinder looks like a Japanese item, as the range of available master cylinders would have been severely limited around that period I'd guess it's probably a CB750/CB500 unit which seem to be 14mm.

I can confirm that the Dunstall master cylinder is from a K1 CB750. The master cylinder kits are readily available so there is no problem in keeping the original master cylinder. i recently purchased a kit. The O ring seals for the screw in caliper plugs are 1/16" larger than the caliper pistons. the caliper piston O rings from memory are only 1/16" thick (or 2mm at the most)
ando

Like Ron said, check the Vintage Brake chart. If it isn't the right size it won't work worth a damn, regardless of the brand name or how big the disc is or how many pistons the caliper have.