TOPIC:

1978 KZ750 Twin. So I am bleeding the front brake and fluid flows but pressure will not build. I had put in a new Master Cylinder kit but since the bike sat for 12 years I went looking for "other" problems. I noticed the reservoir had one open hole and what looked like another hole that was clogged (see picture). I could not dislodge any material with a pick so I decided to drill the clogged material out. As soon as I started to drill it looked like metal shavings coming up so I immediately stopped. I looked into the cylinder bore with a flashlight and could see no evidence of the second hole into the cylinder. I really, really looked not believing there was not some evidence of the second hole. My Honda has two holes in the reservoir well. Is there something I am missing here? Should there be a second hole or is this a different design?

I would only use some hand jet reamer to dis-clog the relief port.

16 piece reamer set . 0.33 – 2.00 mm complete with hand tool and storage case.
Sizes 0.33; 0.4; 0.45; 0.5; 0.6; 0.7; 0.75; 0.8; 0.9; 1.0; 1.1; 1.2; 1.4; 1.6; 1.8; 2.0 mm

the relief hole is VERY small, it has a slightly larger hole counter-bored above it so it looks bigger than it is. The master cylinder will not function if it is clogged. I use a fine sewing needle to clean it out.

I ended up drilling it out with the smallest bit I had, 3/32". Works fine now. I probed several times with a needle for a smaller hole but never did punch through. Should have guessed as the reservoir was full of a solid material, almost like soil, when I first got it open. Thanks for all the help guys!

kzsolo wrote:
I ended up drilling it out with the smallest bit I had, 3/32".

Be careful, 3/32" = 2,40 mm looks like a very big hole you bored out!!!
For safety reasons i hope your next emergency grab onto the front brake leveler not ending up into a pressureless front caliper or fatal accident!!!
I would buy a new MC!!!

Test it in a empty (or near so) parking lot
Avoid surprises under riding conditions on the road
I would say not much to worry about, those hand picks and the such can alter the diameter more than you would believe