Rear master internal diameter.

[sixinoz]

Just had my pitted rear master cylinder resleeved but is leaking badly. Opened it up to find the seal piston was a big lump of brass??? Seals look ok apart from leak.
Can someone confirm that the internal diameter of the cylinder is 16mm? Looks like I will have order a proper kit for it.

20220331_162733.jpg

[CBX-tras]

If you look on the back side of the m/c, it should have "14" cast right into it.

That designates that it's a 14mm bore.

[sixinoz]

Yes - the master cylinder has the "14" on it that's why I was asking. I measured the bore last night with a friends gauge and it was 16mm???
Has the guy resleeved this oversize and that is the reason for the homemade piston and leaking seals?
If that is the case where do I get a kit to fit a 16mm bore and how will it affect brake performamce?

[CBX-tras]

I think locating a good m/c might be easier that attempting to resleeve or locate 16mm seals to fit his homemade piston.
(IMHO).

Even if, you could find the right seals, I believe the amount of pressure to the caliper would cause the caliper to be too aggressive, given the length of the pedal.
On my current build, I've adapted the Ducati m/c to work but, I don't care about originality here. Quite the opposite. Enlarge this, you'll see several differences including the reservoir size and hose diameter. The banjo bolt is a pressure switch for the brake light.:

[sixinoz]

Checked the front cup seal and it is marked 5/8 in. Not quite 16mm and could account for the leak.
Used m/c's without any pitting are hard to find.

[Larry Zimmer]

Something to consider: https://www.cbxclub.com/forum/viewtopic ... 50&t=10394