Topic: Can someone point me in the direction for a master cylinder rebuild DIY?

[rocs]

So I have a couple bikes with either the front brake sticking or no compression at all at the hand brake lever. Im assuming they need rebuilds.

I didn't see one in the FAQ section so was hoping there was a DIY or How to rebuild these front brakes. Hopefully 4into1 will have all the parts needed.

Thanks!!

[Chachi]

Brake FAQ:
http://forums.sohc4.net/index.php/topic,259.0.html

Not a rebuild, but I've had really good luck with these:
http://www.davidsilverspares.com/CB750K3-FOUR-1973-USA/part_123913/

They also have repro caliper bodies if caliper is too far gone too.

[mcinturff]

I followed this video when doing my front brakes.  Came out great.  Good luck!

[PeWe]

Brake FAQ:
http://forums.sohc4.net/index.php/topic,259.0.html

Not a rebuild, but I've had really good luck with these:
http://www.davidsilverspares.com/CB750K3-FOUR-1973-USA/part_123913/

They also have repro caliper bodies if caliper is too far gone too.

I ordered one from David silver AND the cap in oem style that made it look much better
http://www.davidsilverspares.com/parts/by-part-number/partnumber_3826/

[78whiteorbs]

Brake FAQ:
http://forums.sohc4.net/index.php/topic,259.0.html

Not a rebuild, but I've had really good luck with these:
http://www.davidsilverspares.com/CB750K3-FOUR-1973-USA/part_123913/

They also have repro caliper bodies if caliper is too far gone too.

I ordered one from David silver AND the cap in oem style that made it look much better
http://www.davidsilverspares.com/parts/by-part-number/partnumber_3826/

This is the thing to do ....new is always better than rebuilt and there's no cussing involved.

[Johnie]

Really not much to it...the hardest part is getting the cir-clip out of a small area with a snap ring pliers. You can see a pic of that clip on the top left below. Don't be surprised if your master guts look like this when you get them out. Pay attention to how the parts come out and you will be good. I know the Honda kit you have to slide a seal over the piston. Not sure about the aftermarket stuff.

[PeWe]

I still have my old master cylinder that I'll might repair when I have time and parts. When I ordered from Davidsilver the additional cost was not that much more than the repair kit only. Fresh black surface and new lever too.
Do not forget to order the rubber cover over the banjo that might be rotten.

[Johnie]

And to help with the cir-clip I would suggest spraying some PB Blaster in that area once you pull off the rubber cover which would be the first thing you do. Then let it soak overnight to loosen up that cir-clip. I do that on all of them and it sure makes it easier to break it free.

[NobleHops]

Great advice all the way around. With rebuild kits running $25 or more, a new MC with lever for $50 looks pretty reasonable.

If you do prefer to rebuild yours for originality or just fun, I'll add a couple small suggestions: You're going to find a rubber boot around the end of the plunger, it rides in a groove at the lever end, easy to pull off, but way down there in the muck, there is a plain ring holding it in. For starters just grab and tear that boot off, then dig out what tears off and remains down near the circlip as best you can. Now take a small pick with a bent tip and see if you can fish out that plain ring visible in the center of this photo from 4into1 (http://4into1.com/genuine-honda-brake-master-cylinder-rebuild-kit-45530-377-305-cb360-cb400f-cb450-cb500t-cb550-cb750/) and fish out what likely remains of the rubber boot.



NOW, hose it down in there with WD-40 or PB Blaster, let it soak, blast out the yummy gook with compressed air. Wear safety glasses or better yet a faceshield, wrap in paper towel, etc, DAMHIK. Now you can see what you're doing.

The circlip sits in a groove obviously, and it commonly sticks in there. Give it a tap with a pin punch just to jar it free, and see if you can rotate it with a pick. This is made easier by depressing the plunger with your third thumb while you do this. If not, more soaking with penetrants. Once it's free, then its time for the snap ring pliers.

You want these. You want these. Said that twice.

http://www.motionpro.com/motorcycle/partno/08-0279



That new MC from DSS is starting to look damn good right about now, but these pliers are great for other things too.

N.

[70CB750]

Easiest way is to bend the circlip and get it out, can be done with small screwdriver for instance.

[NobleHops]

Easiest way is to bend the circlip and get it out, can be done with small screwdriver for instance.

Agreed, that works, and that's what we ended up doing a few days ago, but we had to get under one end first, and that involved these pliers to get it free of the groove. Once one end of the clip is free, get a pick under it, give it a tug, and watch your eyes, because it can leave the general vicinity at high speed when it gets free of the groove.

One of my early mentors called those and e-clips "Jesus Clips", because he always found himself saying. "Jesus! Where did that clip end up!" :-)

[Johnie]

You have to be real careful if you start bending on that cir-clip in the groove. I had the end break off once and that bugger was still in the groove. Not much to grab onto then. Was lucky and got it out, but very difficult.