Topic: Considering some "upgrades" -OR- Dual disc brakes... or not

[kach_me]

I am considering going to a dual disc brake set up on the front end of 76 K.  Does anyone have experience with this modification?  Is it effective? OR would it be more beneficial to have dual disc (one in front and one in the rear)?

Also, what are you opinions on ventilating the brake discs? 

SK

[medic09]

I think a handful of people here have done it.  Did you search for the threads?  El Cheapo at Anubis cycles even put together the components as a kit a few times.

I've been wanting to do the dual front myself.  No time, no money (now that I just bought a modern bike for the stable).

[Soos]

I don't own a runnign 750, but I have done a dual disk conversion on a '79cb650.

The difference in stopping power is very noticable, and appreciated by me.

If you can do it I would say go for it!
I got lucky and it cost me 50.00 for a bike that had dual disk front end.
Swapped in a day, and am glad I did it.

If I have a choice, all my future bikes will either have, or get modified to dual
disk in the future.

l8r

[jevfro]

I'm also contemplating a dual up front.  From what I've heard it basically doubles your stopping power.  Drilling the rotors will eliminate weight and supposedly make them cool a little faster.  If I do it I will eliminate the speedo drive and use a digital unit (this will simplify things I hope).  Just need to find a good MC for dual discs and an extra caliper set.

[Steve F]

Glad to see you spelled it duAl and not duEl.  I hate it when the brakes are fighting or is it breaks?
Anyway, yes I've done it, and am  happy with it, and it stops really well.  You CAN keep the speedo drive, with a slight modification to the drive plate and the rotor.  You'll need to get some longer bolts too.  I was fortunate to find someone local that had an extra rotor, caliper and all the bracketry that goes with it.  If you need more info, or want to see the mods that I did to the speedo drive and rotor, PM me.
I have a '76 760F, and discovered that the two forks lowers were not symetrical, or in other words, the castings were not mirror images of each other.  I found that the part on the leading edge of the fork where the centering screw and spring attach were at different distances from center, and a 2mm shim was necessary
The photos show what I'm talking about.  I used a master cylinder from a '77 750F, which had a slightly larger bore than the '76, so it made the lever travel shorter, but still wasn't too large to require an extra amount of force to come to a stop.  Maybe there are aftermarket master cylinders that would work better, I don't know.

[kach_me]

I think a handful of people here have done it.  Did you search for the threads?  El Cheapo at Anubis cycles even put together the components as a kit a few times.

I've been wanting to do the dual front myself.  No time, no money (now that I just bought a modern bike for the stable).

Tried to get hold of him via web site email address, but he hasn't responded yet.  I saw the kit and had a couple of ? for him.  It looks very interesting. 

[chippyfive50]

It was the best money I've spent on a bike. If you are not adverse to the loss of your stock master cylinder,  the NISSIN 14mm radial is REAL NICE..   The safety level is WAY UP.
I don't know about a kit, but I spent $135.00 on the NISSIN, $100 on dual stainless lines from HEL.com(nice),$45 on  the "second" caliper and mount, which I did offset, and another $25 on brake pads.
ANYWAY, no regrets...

http://shopping.speedwerks.com/catalog/c0m0bm0b0s1pn0p4182np0

[tgascon]

Just finished my Dual Disk upgrade and WOW what a difference!
75 CB550
The info available in the archives is very helpfull and it really isn't that difficult. Patience is key.
Keep watching Ebay for parts and it doesn't even get too expensive.
Rotor $10.00 (drilled)
Caliper and arm assy $20.00
Master Cylinder 94 FZR with lines $12.50
New seals and bolts, shims and fluid $30.00
Stopping power  PRICELESS!!!!!!!!!!!

[ProTeal55]

I noticed a HUGE difference when I added a 2nd rotor/caliper to the front of my old CB750.
I especially felt the difference when I rode my buddies 750 with a stock setup (almost killed myself )

A dual-disc setup will soon find it's way onto the CB450 (Gonna be sweet to have that much brakin on that little of a bike )

[sandcastcb750]

I think the CB750 with dual discs stops really well. unbelievable. My K1 has it.

You can't use a K0 hub as it is 4mm too wide. I think that is why K1s and later have narrower hub for possible 2nd disc. I think K0 bolts go through the discs work as if it was the second disc, makes it 4mm or so wider. Right side front forks have lugs for the caliper hardware.

1977-78 CB750s have caliper arms that can be flipped to the other side, easier. 1969-76 have caliper arms that require work to make a mirror image job. I guess CB500s and 550s are like the K7-8 CB750s. The metal brake line must be re-curved.

The master cylinder on any CB750 SOHC is sufficient. Get a longer banjo bolt and put two brake lines together.

I have drilled dics. Can't say that it stops better. However, when drilled, two dics weigh about the same as one un-drilled. Think about how much weight a second disc adds.

You can lock-up a rear drum CB750. The front brakes do 60% or more stopping. I think a rear disc does nothing, but it would be easy to take one fron a F model and (god forgive us because the purist won't) put it on a sandcast.

Except for drilling, 2nd disc doesn't cost much and the stopping power is great.

[GNXFan]

sandcastcb750 can ypu please send me some closeup pictures of how you mounted your second caliper arm to your right fork? I also have a K1 that I am converting to a dual disc setup but it seems  that converting the later model K's are easier because they have that T shaped caliper arm that can be used in either direction.

[GroovieGhoulie]

I've heard that the added weight of the second disc and caliper, being unsprung rotational weight, have a negative effect on handling and the added weight also offsets any increase in braking power.  Any truth?  I'll admit, I was quite nearly talked out of front dual disc by this information.

[sandcastcb750]

If you drill the discs, you will have less weight.

In a couple of weeks, I will try to get a picture or two of my K1 with dueling discs.

[jaguar]

isnt the easyest way to do this to just swap the front end off a bike? 
i have a complete dual disc front end off a 78F and want to put it on my 76F.  should be a bolt on upgrade...right?  i also have a complete front end off a late 70s custom that im looking to get rid of

[Steve F]

isnt the easyest way to do this to just swap the front end off a bike? 
i have a complete dual disc front end off a 78F and want to put it on my 76F.  should be a bolt on upgrade...right?  i also have a complete front end off a late 70s custom that im looking to get rid of

Yeah, the front end will "bolt-up", if you don't mind having to use the ComStar wheels.

[eurban]

Yes you will have a fugly comstar up front and a spoker in the back.  Of course you could then go to the trouble of mounting a Comstar with a disc to the back as well but now its become quite a project. . . .

[kach_me]

Has anyone heard from El Cheapo lately?  I sent him an email regarding some items on his web site, but haven't heard back.  I'd like to ask him about the dual disc kit he offers...

[HondaMan]

I've had dual and non-dual on my 750s. Currently, I have gone back to single until I can come up with a pair of drilled disks that will weigh in at 60% or less of the twin setup. The added weight of the discs and caliper hardware really affected the twisty-road handling, which I did not appreciate. On the track, it was invaluable, because the 3-digit speeds made it mandatory. Which, by the way, is how the front hub got narrowed 4mm by Honda: it was required that a street-bike-stock front hub be used at Daytona in those days ("stock" production bike racing rules back then), and Honda wanted to run the 750 in 1970 there (which it did, taking all honors). So, in the late K0, the front hub suddenly changed to the 4mm narrower design, with a shoulder cut on the other side to allow for set-on of the other disc. All that was then needed was another caliper, assembled backward, 3 shim washers (2-4mm thick) for the stock caliper mount, a second hose and a longer banjo bolt, and you were "twinned". I ran mine like that from 1971 until 1979, then went back to the single disc for the above-mentioned street reasons.

[KB02]

A Panic Stop last week made me stop to reconsider a dual disk set up. I know it's not a modern bike, but my Duc could have stopped in half the distance. I actually have most of what I need. I just need a disk and possible a new caliper (I have one, but there is a reason I took it off my bike, you see).

[sandcastcb750]

Greg Mazza drilled my CB750 K1 front discs

You guys can email him for costs

http://www.mginproducts.com/

GMazza@mginproducts.com

[Roach Carver]

Greg Mazza drilled my CB750 K1 front discs

You guys can email him for costs

http://www.mginproducts.com/

GMazza@mginproducts.com

if someone gets a price please post it here.