Topic: Dual Disc Brake Setup Questions.............

[ProTeal55]

Hello ,

I know this topic has prob. been beaten to death , but I had a few specific questions.....

1. I am looking for the easiest , painless way to complete this task. Is their a certian year front end I should start looking for , that will bolt up to my 1972 CB750 ? I know some later year Honda bikes came with dual disc setups. If i accquired one of these front ends , and master cylinders , I would be in the show right ?

2. Any aftermarket companies sell dual - disc retro kits for these bikes ? To maybe use a newer style brake setup ?

3. Along with the lower legs , and discs , would I need to change out my front wheel ? I am thinking I will , because my f.wheel has provisions for only one rotor , not two...

4. On a side note , anyone know of a solid rear wheel that would fit on my CB ? Looking to get one , and have it powdercoated black. I would say to just run a Harley wheel , but I know the axle sizes are different....

[Geeto67]

a 1975-1977 goldwing front end is almost a bolt on. I say almost because if you use tapered headstok bearings you have to use one for the cb750 and one for the goldwing (I forget which ones). I got my 75 goldwing front end off ebay for about $200 tire to top clamp (including GW speedo).

If you want to run dual discs on your cb750 wheel you have to get longer bolts. There is an article in the resources of this site telling you how to do it but keep in mid the parts to get the speedo to work are ultra rare and you will probably have to run without a speedo or make something fit.

For a solid rear wheel an early fatboy rear wheel is pretty close dimensionally (1990-1997 evo ones with the narrow tire), may have to have a custom sprocket made, spacers made, and convert to rear disc. For 1" axle harley wheels you just make a bushing to adapt the rear bearing size to the honda axle size. If you go to an industrial bearing supply house they may be able to find you a bearing that will work with your setup. If you can't find exact, find something close and have a machinist open up the bearing race in the wheel a little.  I have a set of custom centerlines made for a honda chop in the 70's but good luck getting me to part with them (they are a 1" axle but have the bushing and all the pieces to work with honda axles). PM can make custom orders but that is big bucks.

cbr wheels have the same axle size but custom spacers are needed as is the conversion to rear disc. If you have a motorcycle junkyard near you go over with an axle, a dial caliper, and a tape measurer and play around.

You can bolt on any front end you want to your bike if you modify the triple clamps to take the honda stem. That is how I got an fzr600 front end on my kasasaki triple.

[SteveD CB500F]

Go here

http://www.sohc4.us/forums/index.php?topic=259.0

for full description (incl photos) by a member who has actually done this.

[alfabeast]

You'll need a custom part to do a dual brake set-up on a '72, you'll need a right handed version of the little cast piece that secures the caliper (I'm not talking about the piece that is sandwiched in the caliper), later models don't use this part and are easier to convert.

[ProTeal55]

Correct me if I am mistaken , but after reading all of that great info , I am still going to need
a right hand fork leg to mount the actuall brake calliper ? As where the one on the bike now has no provisions
for a caliper..

P.S. - Great step by step instructions

[bryanj]

The RH caliper has the bolt holes BUT there is a braket bolted on that the "Caliper Swinging arm" pivots in and that bracket was only originally made in titanium or magnesium (cant remember which) by Pops Yoshimura for racing and is a "mirror image" of the LH one . Havent seen one for many years. If you get the later K forks you can just fit a complete LH caliper assembly with the caliper transposed. The second disc just needs longer bolts and you can modify the speedo drive plate relatively easily i have a picture of what you need if you email me direct. On top of that you need a Goldwing master, which if you get the one with the brakelight switch you can fit the second lower flexible where the hyraulic switch is on the lower tree

[ProTeal55]

BYRANJ----> Which year lower legs should I be looking for , that will fit my stock fork tubes ?
This seems like the easiest way to go about the whole dual-disc project....

[Geeto67]

Proteal55,

I think thelater k forks bryan is referring to are the 74-76 k4 -k5- k6 where you can just use the Left hand caliper and bracket. I started to do this on my k5 (until I found my goldwing front end) and that is how I was doing it.
 

[ProTeal55]

GEET067--> Have any parts that you arent't using that you wanna part with ?

[alfabeast]

I got one of those RH brackets a few years ago in the UK, some guy was making them for the classic racing scene, problem is I can't remember his name, they are out there though.

Here's my <72 dual disc setup:
http://home.earthlink.net/~alfabike/sitebuildercontent/sitebuilderpictures/sohc42.jpg

[ProTeal55]

I spent the better part of the day today here at work looking online for either a Goldwing front end , or later year lower fork legs , with no luck.

If anyone knows of where I can get the needed parts , please let me know. I really want to do the Dual-Disc conversion to my bike.....

[alfabeast]

Got my bracket in 1998 for about $70 from this place:

B & C Saunders ( England )

Tel:011441451 822397

Not sure if they're still in business.

[ProTeal55]

I got a line on a 1975 Goldwing front end , waiting to hear back from the guy.

Are the fork tubes the same size on my CB and the Goldwing front ends ?
Would I need to get the Goldwing front wheel as well ?

[ProTeal55]

I just took a look at my bike , and their is no difference between the left fork slider , vs. the right.
All the provisions that hold the left caliper on their - are also on the right ...

Does this mean All I need to do is get a complete brake caliper assembly and bolt it up ?

[bryanj]

NO you need that "handed" bracket. Easiest fix is complete forks (not just sliders) from a K4 or later with second caliper including brackets. Send me an email direct and i will mail you a document for 500/550 which is very similar to the later 750. If you go goldwing you need the COMPLETE front end

[Geeto67]

I got a line on a 1975 Goldwing front end , waiting to hear back from the guy.

Are the fork tubes the same size on my CB and the Goldwing front ends ?
Would I need to get the Goldwing front wheel as well ?

The gold wing forks are 37mm. cb750 is 35mm. To put a gold wing front end on your bike you need the triple clamps, complete forks, front axle, and either: cb750 wheel with cb750 discs and brakes, or gold wing wheel with goldwing dual discs and brakes. the offset on the brakes is different so if you use the cb750 brakes you need the rotors. I think the cb750 rotors will bolt up to the GW wheel (which has an aluminum rim BTW) so you can use the goldwing wheel and spacers (with a washer in there for spacing maybe). Personally it is better to get the whole complete front end because everything works together and the calipers are better than cb750 ones.

As for front ends, I have a complete 1975 cb750F front end I am not using. I am reluctant to part with it because 1) shipping a whole front end to chicago is expensive and I don't really want to break up a matched set, and 2) It was one of a pair of front forks I bought to repair my front forks after I had a laydown. I have a buddy who has a stockpile of old cb750 front ends if you want I'll look through what he has for you (I have to go there this week anyway). This way you get just the forks you need and I don't have to part out my front end. 

[ProTeal55]

GEETO67 ,

Thanks for all the help on this ! Email me directly if you buddy has anything that I can use in my quest for the Dual-Discs.

[MRieck]

I have a set of drilled CB750 rotors with bolts. PM me if you're interested.

[Tommy]

ProTeal,
   I recentlly did a dual disc conversion on my 72 CB750, and I used a standard left hand caliper bracket on the right hand side.  Everything lined up well, but i needed to file down the tab that was used to hold the disc splash guard on, as it rubbed the rim.  You wil have to do without the splash guard with this system, but it will work.  I also found that a larger master cylinder went a long way to improving the braking, although the stocker would stop the bike from high speed, but never felt right, it felt spongey to the end.  Don't use cheap hardware store bolts for the discs.  It's your ass, and spending a few bucks more on quality bolts is worth it.  Also, the caliper bracket on the early bikes is much different than the later ones (73 on), just take a good look at it before you go to the junkyard.  Good luck.

Tommy
72 CB750
73 CB750
70 CB350

[ProTeal55]

TOMMY----> Thanks for the heads up on the install.
After looking at my bike , i figured it couldn't be all that hard to just copy the left side setup on the right.
And you proved that !

Have any pics of your new install ?
What Master did you end up going with ?
Please email pics , if any to Saytin72@aol.com

[Tommy]

Proteal,
   Glad to hear it worked out for you.  I ended up using a MC off a 77-78 CB750, it has a larger bore for its dual discs, and looks somewhat like the original.  I don't have any pics, I've been meaning to do some.  After figuring out all the small details, the whole thing seemed pretty easy. Have fun riding and stopping faster.

Tommy
72 CB750
73 CB750
70 CB350