Rear MC spooge hole

[CaptonZap]

Today, I had the honor, well, more like duty, to clean the rear brake system on a 79 Standard.
I few weeks ago, someone was asking about the spooge hole location in the rear MC, and since I was in there, I'll describe it as best I can.
When looking down on the MC as it sits in the bike, on the back side, about the 2 o'clock position, is a 14 mm bolt head. When it is removed, (and you are better off loosening it while the MC is still bolted to the frame), and you have removed the MC, you can look into the cavity under the reservoir.
Looking in, you will see two holes in the wall between the plunger hole and the reservoir hole.
The lower one is smaller than the upper one, and it is about .090 in dia, and leads into the plunger bore. This feeds the piston.
The upper hole is larger, and is about 3/16th in dia. and does not go all the way through. Except for a TINY spooge hole in the bottom of the hole. This allows any leakage past the piston to get back to the reservoir. If it gets plugged, the piston does not retract far enough back to uncover the lower hole, and the pressure in the system is not relieved. And a dragging brake is the result.
I used a wire bristle from a wire brush to clean out the hole.
I removed the reservoir, to get everything clean, and was able to clean the spooge hole with the wire and a pair of needle nose pliers, applied through the chamber under the reservoir. If you do not want to remove the reservoir, you will need a wire about 2.5 in long, to access the spooge hole through the 14mm plug hole. You can fasten the bristle to a nail with solder to get the length needed. CZ

[ViperRon]

If you do not want to break bristles out of your wire brush I have found that the wire used for hanging pictures is great for cleaning out things. You can take a section of it put in a drill and it will clean hoses very well for smaller holes just strip off a wire or two. Most times crud will collect in the hose too and work its way back to MC or into the calliper. The twists in the wire make it contact all sides creating great scrubbing action.

[Cobia]

Metal guitar strings work well also, particularly on carb jets. They also come in different thicknesses.

[Aches n Pains]

Second the guitar string. Buy a set and you've got brake cleaning and carb cleaning wires for life.

[Yard Dogg]

Or you can buy some long sewing needles.

[CaptonZap]

Or you can buy some long sewing needles.

Bad idea.
When cleaning out orifices, you want to use a straight sided wire, especially on jets. Preferably, with a wire softer than the orifice metal. A needle is tapered, and with just a little to much pressure, the needles can start to enlarge the diameter of the hole, thereby altering the function and metering ability.
I have, in the past, suggested the use of a safety pin as a method to locate a spooge hole, but that was just to find the hole, and a wire should be used to clean it out.
One could argue that a spooge hole is not a jet, and would not be harmed by a bit of enlargement. I would argue that the factory made it that size for a reason, and altering it may have unknown consequences.
Besides, it is better to get in the habit of doing things correctly, rather than kludging things up. CZ

[Yard Dogg]

That's where finesse comes in.

[jrm000kc]

Rear brake

I took my caliper apart last week and found a slug of dirt/old brake fluid living inside the caliper. Got it cleaned up and re-assembled and wow what a difference.
However when I first take off after the bike has been sitting I'll hear the brake pads slightly sqeaking. Hitting the pedal makes the noise go away. I suspect the piston still isn't retracting like it should. When I got home today I put it on the centerstand and spun the rear wheel. It'll spin, but only a half turn at the most. Not sure if I'm feeling the resistance from the drive shaft or if my brakes are slightly dragging. Rotor feels warm, but I can't tell if it's from braking while riding or a drag problem.
It's probably high time to clean the MC out if the caliper was filthy. Any thoughts?

[jetmechmarty]

Replace the brake fluid. That may take care of it for you. Just get a fresh bottle of fluid and bleed it through. Of course, if you really want to rebuild your master cylinder, it can't hurt, unless you mess it up.

[jrm000kc]

Yea I'll give changing the fluid a shot and see how things go then. Probably go ahead with an MC cleaning this weekend if possible. Thanks!

[DGXSER]

The desenting opinion

For the time involved, and the cost (practically free), since you can re use the parts, I would suggest rebuild it. If there was more than dark fluid in the caliper, the same crap is in the MC

[skids]

I had an xs11 with a locking rear brake and I was lucky enough to free it up with a fluid change. That was about 8 years ago...

[Ken Talbot]

Today, I had the honor, well, more like duty, to clean the rear brake system on a 79 Standard.
I few weeks ago, someone was asking about the spooge hole location in the rear MC, and since I was in there, I'll describe it as best I can..... CZ

There's some photos in this thread .