1993 K1100RS master cylinder

Wanna talk BMW K bikes? Here's your home.
Post Reply
dwerbil
Moderator
Posts: 2856
Joined: Tue Aug 03, 2010 10:58 am
Location: Round Rock, Texas
Contact:

1993 K1100RS master cylinder

Post by dwerbil »

Just finished putting in a couple new front M/C piston seals and was bleeding the brakes when I noticed brake fluid was
spraying up a bit inside the fluid reservoir. I emptied same to see a small pinhole that would squirt fluid when the lever was depressed. Pinhole is inside the circular dimple....

Image

I don't think this is normal behavior since a hydraulic system is closed. Can I epoxy this closed or JB Weld it, or am I screwed to replace this M/C?
Image

Click for pics
04 R1150RT ~ 78 R100/7 ~ 84 RS ~ 93 K1100RS ~ 65 R60/2
Randy in Round Rock
robert
Posts: 471
Joined: Sun Jan 30, 2011 4:03 pm

Re: 1993 K1100RS master cylinder

Post by robert »

It's normal and it needs to be there. Look at it -- it was machined there for a reason.
User avatar
George Ryals
Posts: 510
Joined: Tue Aug 03, 2010 10:22 am
Location: Stone Mountain, GA

Re: 1993 K1100RS master cylinder

Post by George Ryals »

That hole lets fluid back into the reservoir when the lever is released. Since the piston seal comes back to clear the hole when the lever is released, the initial movement of the piston going forward momentarily squirts fluid before the hole is covered by the seal.
Smile it's contagious!
'74 R90S, '67 /2 Conv w/sc, '66 R50/2
'74 Harley FXE, '72 Harley FLH w/HD sc
'69 BSA 441 Victor Special, '74 R90/6 Basket case
'85 R80RT wreck for parts
dwerbil
Moderator
Posts: 2856
Joined: Tue Aug 03, 2010 10:58 am
Location: Round Rock, Texas
Contact:

Re: 1993 K1100RS master cylinder

Post by dwerbil »

Well, I'll be. Ya' learn something every day.
Thanks for the info.
Image

Click for pics
04 R1150RT ~ 78 R100/7 ~ 84 RS ~ 93 K1100RS ~ 65 R60/2
Randy in Round Rock
Post Reply