Topic: CB750 K7 - which way does brake piston go in?

[timmerk]

I just rebuilt my front brake on a K7, but now I'm starting to doubt myself. The K7s don't have a big hole on one side of the piston - they are flat on both sides, with one side being a smaller diameter (see picture below.) Should the side with the smaller diameter be against the back of the pad, or go into the caliper first when dropping it in?

Also, the white plastic ring that comes in rebuild kits - it wasn't in the parts diagram, so I assumed it was for another model, and didn't use it. Now I see from the aftermarket rebuild kit description page that I should have placed it between the piston and the pad. So now I'm taking off the wheel, unbolting the calipers, etc - I just wanted to make sure I have the piston in the right way so I don't have to do all this for a third time.

[bryanj]

 ;)never seen a piston like that on a 750 sohc, later models had "dust seal" as well as fluid seal but piston shouldnt be used as with new pads piston can go in too far

[Don R]

 That's the center bleeder piston. I've owned a couple and recently rebuilt one but am reluctant to say which is correct. The K7 caliper is same as F0/F1 maybe the info will be there.
 Edit' didn't find it but I'm going with smooth side to the fluid, stepped side towards the pad.

[david 750f]

Thats the same piston as the 75/76 F's . Larger diameter towards the pad.

[scottly]

No, the smaller diameter at the top of the pic goes against the pad!!

[Don R]

 I took one apart and looked, it was what Scottly said.  If that end is a pressed in cap you wouldn't want fluid getting in there. 

[timmerk]

Thanks for the replies so far! Hmm, to add to confusion, here is what one seller says on https://4into1.com/front-brake-caliper-rebuild-kit-honda-cb750/: "The darker side of the piston with the indented ridge faces the brake pad."

But, I can interpret that sentence two ways:

*   There is an indented circle area on the larger diameter side.. this could be an "indented ridge."
*   There is also a smaller diameter side, which could be called a ridge.

(Mine doesn't have a darker side.)

It's also hard to tell from the diagram (diagram is from 76 750F) below. But the service manual makes it look like the smaller diameter end goes against pad (also below.)

But, I think the general consensus is the smaller diameter side is on the pad side.

[david 750f]

No, the smaller diameter at the top of the pic goes against the pad!!

Sorry Scottly, had it backwards. Brain f*rt..