Topic: master cylinder upgrade decision

[lendog]

I'm currently tearing down my controls/master cylinder to to install some drag bars. I have a 77 cb750f. I'm in the process bringing it back to life. I have not had it on the road so i don't know how the brakes are. The piston in the m/c seems to be working ok. I was thinking about buying th rebuild kit....but then reading all these posts about upgading to a more modern sport bike m/c sounds interesting to me. The rebuild kit costs $35.....I called my local salvage yard and they told me they have a couple of CBR's lying around. I don't know what years they are I'll have to go and check them out. I'm assuming I'll be able to pick up one of those m/c for about the same price. As you know my cb is a dual disk stock set up. Am I better off going for the upgrade as opposed to the re-build? Especially since I'll probably have trouble fitting the stock m/c on these tight dragbars. Secondly...if i decide to go this route what's involed in actually making the conversion? I've been searching faq's/ archives for an hour now and I can't seem to find any tips or pics showing the actual process. If anyone has pics or could explain the proceess would be great. Thanks in advance

[MCRider]

I'm currently tearing down my controls/master cylinder to to install some drag bars. I have a 77 cb750f. I'm in the process bringing it back to life. I have not had it on the road so i don't know how the brakes are. The piston in the m/c seems to be working ok. I was thinking about buying th rebuild kit....but then reading all these posts about upgading to a more modern sport bike m/c sounds interesting to me. The rebuild kit costs $35.....I called my local salvage yard and they told me they have a couple of CBR's lying around. I don't know what years they are I'll have to go and check them out. I'm assuming I'll be able to pick up one of those m/c for about the same price. As you know my cb is a dual disk stock set up. Am I better off going for the upgrade as opposed to the re-build? Especially since I'll probably have trouble fitting the stock m/c on these tight dragbars. Secondly...if i decide to go this route what's involed in actually making the conversion? I've been searching faq's/ archives for an hour now and I can't seem to find any tips or pics showing the actual process. If anyone has pics or could explain the proceess would be great. Thanks in advance

I've used 2 junkyard MCs, one from a Kawasaki and one of unknown origin, but from a twin disc bike. Very happy with both, luck of the draw. Really makes the difference from a single disc bike to a twin disc. Yours is twin to begin with, but still...

Besides the physical problems of size and shape, they usually use the same banjo bolts etc.  Bleed it and go.  There can be issues with the ratio and in some cases I've heard the feel is not good. Trial and error.

The biggest issue may be the brake light switch. I don't know your bike to know if it is built into the MC or is located elsewhere. Regardless should be a simple wiring issue.

I've got an early VFR MC for current project, not expecting any problems as i have above the tank, but still low, bars.

[lendog]

My brake light switch is in my m/c. Are the modern m/c brake light switches also intergrated into the m/c?

[MCRider]

My brake light switch is in my m/c. Are the modern m/c brake light switches also intergrated into the m/c?

Yup, mostly. Since the late 70s (evidently) forward.

[lendog]

So this upgrade sounds simpler than I thought. As long as the new m/c fits a 7/8 bar and the banjo bolt fits It should be an easy swap. Just figuring out the brake light switch afterwards. Thanks Mc.

[MCRider]

So this upgrade sounds simpler than I thought. As long as the new m/c fits a 7/8 bar and the banjo bolt fits It should be an easy swap. Just figuring out the brake light switch afterwards. Thanks Mc.

Yup, piece of cake. All jap bikes are 7/8, all banjo threads the same (I think, mostly) its the size and location/tilt/etc of the reservoir that may be a catch.

You're welcome.

[GoatBaSS]

Some of the bolts from other bikes may be threadded with different size threads. Take the MC bolt with the housing. The hoses should be common.

[fishhead]

  On the bottom of your stock master cylinder it should be marked with a size. Idealy, you would want one the same size as your stock master. The CBR master cylinders come in many sizes (1/2-12.7, 14mm and 5/8- also marked on bottom) so getting one only based on the CBR application could get you one that is great or not so great.
 Most CBR masters come with an adjustable lever that adds another "level" of adjustability to the front brakes.
 Most masters have 1.25 banjo bolt pitch. Some have 1.00 pitch. When you get the master, also get the banjo bolt that was mounted on it to be sure it will have the correct threads.

[eurban]

Just my opinion . . .I like the looks of the old MCs much better than the plastic modern ones.  They perform pretty well too when they are rebuilt, stainless steel lines are used and the system is properly bled.  Here's a pic of the 77/78f MC used on my 78K with a GL1000 dual disc front end and drag bars .  . . . .PS don't throw away that F model MC if its in good rebuildable condition.  They are hard to find!