Front master cylinder 75 R90S

Need a master cylinder for a 75 R90S,mine is too pitted to rebuild although I have a new rebuild kit. If you got one let me know and thanks.

Mark Frappier 800 528-5235 give him a call. He did my 75 R90S and it's been leak free and stopping good for at least 10 years. You're welcome.

Yup, good time to get it sleeved down to 14mm and improve your braking at the same time

Will do and thanks

Is the collective wisdom that 14mm is the magic number for twin 38 and 40 calipers?

Yup, better feel. Change to braided lines, good pads and you’ll def notice the difference

How’s the lever travel with 14mm working twin calipers?

Yessir!

Installed Speigler lines first thing

No issues with the lever travel - there's sufficient room for the increased throw, which is not excessive.
区别是:stoppies似乎达到able.

+1 Mark Frappier

1976 R90S: where have you been getting your 14 mm parts kit (piston, seals, orings, whatnots)?

part # 34 31 1 234 926
MAX BMW lists it for $78.95 - $11 cheaper than Bench Mark Works where prices are often lower.

Problem is no kit comes with the spring perch, which is sized for the bore and spindle.
That small but necessary parts needs to be cannibalized off a junk MC - I may be able to help.

spring perch there: you want it.



that's a 14mm dual outlet MC but the bore needs work.
unused seals on that shiny spindle.

Is this the part between the spring the spool? Are you saying you have one you can spare?

Yes

not one to spare, just the one for the 14mm master cylinder above.
That MC is a spare but it's not much use without the perch.

Someone dealing in good-used parts may have a box of MC stuff, ask around?
Some years ago I sourced the spring perch alone from Larry at Stoner's Beemer Stash. He had a box of MC odds & ends.
Alternatively, it would be fairly simple to turn one on a lathe.