Topic: brake interchangability

[afkrejci90]

I'm looking to get another caliper for a dual disc setup on my 78 CB750K, will super sports of the same year be compatible?

[scondon]

Pretty sure the caliper on the super sport is not the same as your 78 k. What parts are you using to convert to dual disc?

[bollingball]

I think the master cyl. would need to be changed also. Most people go with the old Gold Wing front ends not sure what year.

Ken

[afkrejci90]

Looking at the picture of the caliper I can tell its definitely not the same.  They come in a pair, so my question is would they be able to bolt onto the forks or would I run into other unforeseen issues?

[scondon]

Looking at the picture of the caliper I can tell its definitely not the same.  They come in a pair, so my question is would they be able to bolt onto the forks or would I run into other unforeseen issues?

They would not be able to bolt onto your forks. Hard to say which issues are unforeseen without knowing which of the many issues you have already accounted for. If you describe your plan for converting to dual disc you will likely get more response that will be useful

[afkrejci90]

Ok I will just have to look for a K model caliper and do setup that way.

[bjonesin]

My understanding of this issue is that you literally wont be able to fit another assembly with the stock K setup. The reason that people use Goldwings in the first place is that their triple trees are wider and bold directly on.This wider triple tree makes the space between the forks wider. Wind enough to fit the extra caliper and rotor. The current master cylinder on the K models, the plunger inside of it is designed to operate one caliper. Goldwing plungers are bigger and designed for two.

[RSchaefer]

I am doing the dual brake setup on my '75F.  The '77/78F's have the Comstars and a different setup for the front brakes from the spoke versions.  The right hand fork tube should have the tabs for the 2nd caliper.  Any front rotor from any CB750 will work (not the Comstars).  You need to get slightly longer bolts to go through the hub and catch the 2nd rotor.  Hondaman recommends using the stock master cylinder, no need to go to the GL master cylinder or front end.  Get a longer bolt for the front brake switch and another copper washer.  Biggest issue is modifying the speedo drive, a guy on the forum sells the adapter.

Here is the link from the forum (http://www.sohc4.net/index.php/dualdiskconversion-cb750/)

[scottly]

The K7/K8 used 42.8mm (actually 1 11/16") caliper pistons, compared to the 38mm pistons in the earlier models. The stock 14mm piston MC works fine, IMHO, but if you want a firmer lever, you could use an MC with a larger piston.
The speedo drive adapter you are referring to, RS, is for the early models; Honda modified the drive at some point. The most elegant solution I've seen for the later drive is to machine the back side of the disc carrier to fit over the drive plate.

[Old Scrambler]

Your '77 K does not have a lug on the right for a second caliper.  The easiest way I know of is to source a later dohc 750F front end. You will still have to machine the speedo drive and get the bolts to fit your stock wheel.

[afkrejci90]

Theres already mounting tabs on the right fork for another caliper.  I know it won't be as simple as throwing parts on there, it will take a little modification.

[750K]

Correct me if I'm wrong but don't the rotors on the earlier 750's have a different bolt pattern?i know the F's have a five bolt caliper and the 77-78K has a six bolt caliper.

I was talking to a guy on Flickr that did the front dual conversion to his 74 750 and he machined the speedo hub to fit in the center of the new rotor which bolts right up the the stock rim. Flipped a caliper onto the other fork leg, some spacers and the bracket were needed. Used the stock master cylinder and plumbed a dual brake line and it worked and looked great. If I remember correctly the 77-78 right fork leg has the mounting tabs for the caliper but the holes weren't drilled out.

[scottly]

All of the 750 K rotors are the same. The 77 fork leg has the tabs already drilled and tapped. I did this upgrade about a year and a half ago..

[afkrejci90]

Just looked at the forks today and the holes are already drilled and tapped.  Just need to mod the speedo drive and mount another caliper.

[Old Scrambler]

If you have the lugs..........Use the K parts..........My '77 K did not have lugs.......but now that you guys made me think about it..........the forks must have been changed because it had air-caps and the threads were different.