Topic: Who's done the old dual disk setup

[xfactor]

I was wondering if the stock mc, on the 76 750f is powerful enough to support the dual disk setup. I will also be upgrading to some ss lines to help improve the stopping power.


Croix

[HondaMan]

I was wondering if the stock mc, on the 76 750f is powerful enough to support the dual disk setup. I will also be upgrading to some ss lines to help improve the stopping power.


Croix

Yep. Did it when I lived back where you are now! The SS lines will reduce the lever travel and "firm it up" a bit, but I could still easily lock the front with the stock rubber hoses and the stock master cylinder.

[DH]

Hondaman, along these same lines, would it be an advantage to use 2 550 disks and calipers on a 750k? I know there'd be less surface area brake wise, but it seems like it'd stop better than a single 750 disc set up and be lighter than a dual 750 setup. Your thoughts?

[fatmatt650]

Does anyone know of a "bolt-on" option on this bike? Every dual-disc bike I've seen has them mounted behind the fork. My 76 750f would benefit from a little better stopping power, especially now that rear-sets have dramatically decreased the stopping power due to decreased mechanical advantage of the shorter lever and linkage. It looks as if another rotor and caliper should bolt right up but I have no idea what to use.

[fatmatt650]

Okay, I swear I've searched this a billion times but I just now found this - http://www.sohc4.net/index.php?q=content/dual-disk-conversion-cb750
Is this using another of the same caliper that I already have or do I need to source a right side caliper?

[scottly]

Every dual-disc bike I've seen has them mounted behind the fork.

The fork legs were swapped from side-to-side. Common mod back in the day on the Honda's.

[scottly]

Is this using another of the same caliper that I already have or do I need to source a right side caliper?

Sorry. I didn't bother to read your link, but to change a left side caliper to a right side one, you merely remove the two bolts that hold the two caliper pieces together and swap them on the arm. Instant right side caliper!

[fatmatt650]

Thank you Scottly! I just assumed it COULDN'T be that simple! Now my next question. How universal are these calipers? Can anyone tell me what models to look out for/search on ebay to find the correct caliper/arm or better yet, anyone have what I need and want to part w/ it?

[xfactor]

Thank you Scottly! I just assumed it COULDN'T be that simple! Now my next question. How universal are these calipers? Can anyone tell me what models to look out for/search on ebay to find the correct caliper/arm or better yet, anyone have what I need and want to part w/ it?

You either want to go with a caliper off a75-76 cb750f or I believe a k7 or k8 caliper. This is because the early f models have a bigger piston so you want to go with one with a similar size piston, obviously, and I believe the later k's used the same size piston as the f.

[seaweb11]

I would suggest putting a wanted add in the "parts wanted section"
I did yesterday and have already had a response and paid a member here for the K8 brake caliper and pivot I needed for my next dual set up.


P.S. I plan on using the stock m/c.

[Don R]

76 F with a 75 F caliper on the right side, I have not hooked up the brake line yet so I can't report on the stopping power. It took two extra disc fenders and some fabrication to make a right side one. i just thought it would look stock that way.


I used 5/16" x 4 1/2" (I think) bolts and thin poly lock nuts on the rotors. Check length before you buy. They fit snugly and work fine.

[fatmatt650]

Thanks guys. I love this forum!

[Don R]

If you switch the calipers to the rear you need to drill the fender mount bracket and bolt it back on facing the other way. I have used small stainless bolts and polished the heads a little.

[laminarflow]

I too was worried about the unsprung weight on the front and went with a dual disk and 550 caliper setup.  I just sent the rotors to Scott (formulasuper) to be drilled and blessed holy.  He has some neat drilling options which, at a minimum, makes the whole setup lighter.  It also looks cooler (the engineer in me likes this part as well).  I found this forum to be an invaluable resource when I thought about making this brake change.  I also found Hondaman's book to be crucial, at, well, everything.  Buy it and learn--it was worth every penny.   

[scottly]

I believe a k7 or k8 caliper. This is because the early f models have a bigger piston so you want to go with one with a similar size piston, obviously, and I believe the later k's used the same size piston as the f.

My K7 caliper has a 42.8 mm piston. The older K calipers had 38 mm pistons, I believe. Don't know about the Fs

[Don R]

75 and 76 F's had the bigger piston also. Identified by the centered bleeder location I think.

[fatmatt650]

When fiddling w/ my 76 cb400f today i noticed that the front brake looked very similar to my 76 cb750f. I didn't disassemble to take proper measurements but I did bust out the calipers and check it as best I could. I'm pretty darn sure it's the same thing.
 
Compatibility list
----------------
77 cb750k7
78 cb750k8
75, 76 cb750f
75, 76, 77 cb400f (I'm pretty sure)

Anyone have any additions/corrections?

[scottly]

matt, what is the center-to-center distance of the 2 bolts that hold the caliper to the arm on your 400? On my K1 and my K7 750 calipers it is 1.97".

[fatmatt650]

matt, what is the center-to-center distance of the 2 bolts that hold the caliper to the arm on your 400? On my K1 and my K7 750 calipers it is 1.97".

I'll measure tomorrow or Wed. and get back to you.

[seaweb11]

Anyone have an online supplier I could order the longer 6x8mmx110mm bolts for disc?

[fatmatt650]

I would suggest putting a wanted add in the "parts wanted section"
I did yesterday and have already had a response and paid a member here for the K8 brake caliper and pivot I needed for my next dual set up. Grin Grin Grin Grin

Mind if I ask what you payed?

P.S. "how much!?" - Borat

[rangelov]

I got my bolts from Metrix unlimited in Warren, MI.

You could also use 5/16 bolts, they are close enough.  There is only .003" difference in diameter.


SHAMELESS PLUG:
http://forums.sohc4.net/index.php?topic=76835.0

[seaweb11]

I would suggest putting a wanted add in the "parts wanted section"
I did yesterday and have already had a response and paid a member here for the K8 brake caliper and pivot I needed for my next dual set up. Grin Grin Grin Grin

Mind if I ask what you payed?

P.S. "how much!?" - Borat

Not enough to really think about

[seaweb11]

I got my bolts from Metrix unlimited in Warren, MI.

You could also use 5/16 bolts, they are close enough.  There is only .003" difference in diameter.


SHAMELESS PLUG:
http://forums.sohc4.net/index.php?topic=76835.0

This place? http://www.metricsunlimited.com/

[wookie]

When i was looking for parts on my swap the calipers i chose had a rebuild kit available on ebay. The guy sells a new stainless piston and all nos parts.  AFAIK he only supplies for this caliper though.

 

FWIW the lines are now on the outside of the forks.