I know there has been much discussion and different upgrades around for the stock master cylinder
here is my 1/2" piston assembly that I'm working on, uses the standard rubber boot.
your thoughts.

More info please.

not sure what you want to know.
if all proves to be good after testing then I would offer the complete piston assembly for sale,
I could also supply the reducing sleeve and 2 required drilll bits, but the purchaser would have to drill the 2 holes in the sleeve after fitting with Loctite.some may object to the fitting of the sliding fit sleeve with loctite, but as far back as I can remember brake mastercylinder shops that I know of have been fitting them with locktite.
the whole idea is to retain the stock mastercylinder but have decent brakes.
for those not worried about the stock look I'm working on a specially cast fork slider to acommodate a 6 piston Tokico caliper with 320mm floating disc. a very easy bolt on kit also.

Looks trick, just don't reproduce the factory tiny restrictor hole as non of the resleeve jobs have any and I'm *very* pleased by factory size piston w/o the restrictor. I've also 12 mm resleeve experience to compare. I assume yours is SS so no more rusting in the bore issues.

sleeve and piston can be made from any material , I'm sure everyone has different opinions on which parts should be made from which material. at this stage the material is not an issue

I had my Mk3 master cylinder sleeved to 12mm, it works very well even with the stock caliper and disc. (and good pads)
The place that did it also locktighted the sleeve in.
One thing that wasn't so good was the lump on the lever had to be filed down as the new piston seemed to stick out a little further.
They made the piston from brass and the sleve from stainless.
graeme

madass140 wrote:not sure what you want to know.

How about what seals are you using? Are they readily available?

Hi GRM I will post some pics of what I did to get the lever parallel to housing so the lever didn't stick out after my upgrade. It involved drilling and tapping a very small SHCS (Allen bolt) into the lever mount in a countesunk hole and then adusting it to take any play out of the lever so all action on the lever is positive pressure and you can feel the tension on the pads/disc at all times, ie no free play when you first grab the lever.First pic it is a little hard to see , but it is painted black under the end of the lever
Regards mike

Mike, same as early Brembo's on bevels.
But you have to be carefull that the cylinder pressure releases
thanks
greame.

Thanks Graeme, reason I used a threaded SHCS, can adjust accordingly if necessary, tested it against back pressure cylinder as I did'nt have the slave with me, so far so good, will know in a few days when it goes back on the bike, tiny hole covered by the lever if not able to use it!!
Regards Mike

Hi Madass,

I have made my own sleeve and piston. I used bronze for the piston & stainless for the sleeve. I did find it fun drilling the ports, in the end I bought a couple of carbide tip drills. I ripped off the concept of holding in the sleeve from Old Brits, and providing extra support for the piston, by doing away with the OEM rubber boot and machining a aluminium bush with a slot in it for the lever. This locks in behind handle bar mount bolt. The sleeve was green loctited also, but this gives extra security.
Also as someone else elluded, you need to play around with the piston lenght to get a nice lever feel, same lenght as old 5/8 piston means a little to soggy feel, too much and you risk brake lock on hot days with thermal expansion. Ask me how I know, NOT.
The guy that has taped in the grub screw, I would like see the details if possible.

Cheers Richard

yes Richard, drilling the ports is a concern, with an alloy sleeve its easy to drill and debur on the inside, people seem to rave about stainless sleeves but remember that all master cylinders are alloy anyway, so fitting a sleeve made of a good grade aluminum is an improvement on the standard casting.
I made my piston the same length as the Norton. I will test this first and go from there, this all takes time to get it right .
remember things such as differnt pad material etc can give different feedback to the rider with the same master cylinder

Hi stockie, it was me across the ditch with the grub screw, it is a 10-24 SHCS, you could use a 8-32 if need be
RGM kit gives you a lever adjuster for the plunger/piston, but that always pushed the lever out further away from the h/bar, this just takes the slack out of the initial pull
Regards Mike

Mike, sweet, now I understand. I looked at putting a grubscrew in the lever, where it contacts the piston. To take out some mush, but I was worried there was not enough meat to tap into. But you idea might get me there, will investigate.

Cheers Richard

I've read about adjustable set screws in levers for over a decade now so almost routine to some. Main issue to be cautious of is to leave/allow room enough for piston to retract enough to bleed/relieve fluid pressure on lever release when in hot sun shine or hot use, or can lock right up w/o a hand on the lever or stay locked up letting go of lever. This is not something you will discover at home or shop so can catch ya out in bad surprise, so highly recommend a hair dryer on the m/c *and/&* caliper till too hot to touch test. There Is No Warning, one fine function after another then LOCKed! Same with fluid loss, perfect function no hint till suddenly total lost of brake.