1993 K1100RS master cylinder

[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....



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?

[robert]

It's normal and it needs to be there. Look at it -- it was machined there for a reason.

[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.

[dwerbil]

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