Topic: question on master cylinder repair kit

[ToddR]

Please help and my apologies if this is in the wrong area for questions. I am rather new, just today as a matter of fact. I have a 1977 CB750K(K7) I have been restoring this bike now for about 3 months and am coming to the end. Two problems, both in brake areas, the first is the master cylinder repair kit I bought, the question, "is there a how to place to find out how to put the bugger back together? The next is I have a caliper with a frozen pad and piston that I cannot remove. It is separate from the bike obviously, for the master cylinder is in pieces. Appreciate any help anyone can lend me. Take care and safe and happy holidays!!

ToddR

[climbingaz]

I'm pretty much in the same boat with my K8.  Give us some tips guys!

[zzpete]

An air compressor should blow the puck out of the caliper (be careful). Heres a video of the master cylinder rebuild process. What I have always done is drill a hole in the bottom of the mirror hole and put a finishing nail in there to hold down the piston while I'm taking out the clip. Hope this helps!

http://dotheton.com/index.php?topic=4114.0 

[Alan F.]

Have you downloaded a manual for your bike? Click the link at the top of the SOHC Bikes forum and download the right one for your bike, then look for an exploded diagram of your master cylinder.

To remove a stuck caliper piston there are several methods, the search function works.

My method of choice is to rebuild the master cylinder, then hook it all back up to the caliper, fill the reservoir and slowly give the lever short strokes watching bubbles rise from the "tiny" hole at the bottom of the reservoir. don't let the reservoir run dry as the brake fluid is slowly pumped into the caliper. Leave the bleeder screw on the caliper closed and just pump the lever slowly and gently until the lever stiffens up, that's when you've got most of the air out of the system. This is where I'll place the caliper in a large coffee can and notch the lid so that the line can exit. I'll place my foot on top of the can and keep pumping the brake lever, this will force the piston out of the caliper and it'll also flush out some of the crap that's probably in there too. the coffee can/lid/foot on top will help contain the whole mess when the piston is forcefully expelled from the caliper, don't underestimate the force a squeeze of that brake lever can exert.
Alan

[MCRider]

re; removing the stuck piston, and pad. If you're replacing the pad, I'd try to remove it first, with wide open pliars, or lever of somekind. About 80% of the time you can stick an air hose, as proposed, to the brake line inlet port and blow the piston out. If its going to come that way, it will come flying out, so aim it into a towle or outside or something and keep your face away.

For the ones stuck even harder, remove the end from the hose of a pump style grease gun. Thred it into the MC, the threads aren't the same but you can catch a few threads and that's all it takes. Pump away, the piston will move a slight amount with each pump, after filling wiith grease. But surprise it will come out this way. Then clean up the grease.

[ToddR]

Thanks so much, the video definitely did the trick. Appreciate the help. This is a terrific site!

ToddR