Topic: Master cylinder with built in switch - what is this?

[zabzob]

Hi all,

I'm resurrecting a 1975 750K. Fired it up for the first time on Friday, which was very exciting.  Now that the carb rebuilding and rewiring is done, I'm moving on to brakes.

While researching here I found some steel brake lines being offered by Slingshot Cycles. The single hose setup appealed to me, and I noted that bypassing the 3-way connector would require a new master cylinder with a brake light switch built in. Then I thought... I already have one of those. That's groovy and all, but I purchased a master cylinder rebuild kit a while back on account of the brake fluid having leaked everywhere, and now I'm not sure if I can use it.

Can anybody tell me what this master cylinder setup is? Did the stock master cylinder setup come with a place for the switch connector? Think I could use the stock rebuild kit on this, since I'm assuming the connectors for the brake line are the same diameter?

[mjstone]

Don't know about that master cylinder, but you can buy a banjo bolt from Slingshot Cycles that has a switch built in just for this purpose.

MJ

[GammaFlat]

78K (CB750) models had the switch in the MC.  I bought one specifically to do what you're talking about.  In terms of compatibility with rebuild parts.... not sure.  I think the 77 and 78K MC has a different length of piston?! but all else may be the same?! hmmmmmm. 

[Mandic]

my 77F has the same style master cylinder with the switch mounted to it.  The piston is a different bore than that of a K bike though.

[zabzob]

After much struggling, I managed to get the master cylinder apart. The piston looks to be the same bore. Am I being naive, in that I'd only be able to measure the difference with a micrometer?

The rebuild kit parts are all exactly the same as what I just took out of there, with the exception of the space between the two rings of the piston. Any idea how this will affect things?

[zabzob]

Instead of chancing it with a slightly different piston, I guess I could just clean up the old one and use the new seals and clips (which are all identical.) Any problem with that?

[Nikkisixx]

I'd be a little leary of mixing and matching parts.  If the piston is in good shape then reusing it might be a better option.