TOPIC:

i have a 78 kz650 b2a. im thinking id like to add the second disc and caliper on the front and im wondering from other members is it worth the trouble? also i cant find a rebuild kit for the current 1/2 inch master cylinder and i have a rebuildable 5/8 master to rebuild ( kit coming ) so this may help me make this decision. all else fails ill sell the calipers ive gathered and am going to rebuild and press on...whats a set of rebuilt calipers worth these days anyway?? and advice would help guys...thanks...steve

all depends on your riding habits. a hard rider, probably would help. day to day rider with no hot-rodding like me? would'nt need it.

I upgraded the 79 and 80 750 twins from single to dual disks, and in my opinion it was well worth it. With the dual disk I make the front tire howl when I slow to turn im my driveway, and with the single disk I had to start slowing much sooner or overshoot the driveway (not a good idea since my driveway is on a State Highway).

The diadvantage is more weight on the front end.

Not worth the extra weight in my opinion. The stock single piston calipers are heavy, as are the rotors. You would be better off adapting a twin or four piston caliper from a modern bike. It's not that hard to do and the performance will be better than two stock units.

can you switch to a metallic/more aggressive brake pad? it made quite a difference on my car.

duncan wrote:

can you switch to a metallic/more aggressive brake pad? it made quite a difference on my car.

You can, but I'd much rather replace pads than rotors and the aggressive pads will eat a rotor.

Post edited by: steell, at: 2006/01/14 20:31

i prefer dual discs on the frontend they stop much better especially with a drum rear brake which is of little use in my experience!if you are worried about weight you can drill the rotors which saves weight and also makes them run cooler!goodluck,happy wrenching!

The weight is a factor - even to the point of needing to change the fork oil weight in the forks.

If you go down this path, there are different thickness rotors to consider.

Most of the earlier bikes with single disk have rotors that're 7mm thick (and they are heavy). Most double-disk setups use 4.5mm rotors. There are some exceptions - the double disk add-on for Z1's and KZ900's used a second 7mm disk rotor. Drilled rotors came stock on some models - this makes the rotors slightly lighter.

Make sure you go with a master cylinder for doouble-disk - they use larger pistons in the master cylinder.

Make sure you go with a master cylinder for double-disk - they use larger pistons in the master cylinder.[/quote]

did...ordered the kit from you !!! im making this decision partly because i cant find a rebuild kit for the b2's single disc master and i have all the other parts needed to do it anyway...including two extra calipers that ill probably put in the classifieds when im done with this project. if i decide to go back to one caliper in the future how will that work with the 5/8" master?? thanks for all the advice guys...steve

Post edited by: fixer5000, at: 2006/01/15 08:38

The 78-79 KZ750 twins fave a 5/8" master cylinder with a single disk front brake stock. Jeff is right about the heavy single disk rotors, I used two rotors off a KZ650 dual disk model because they were a lot lighter.

that can come in handy if you dont like doing wheelies! most pople arent going to ride their bikes hard enough to notice the extra weight from thicker rotors but if youre worried about it you can have them turned down and drilled .im one of those sick,sadistic types who likes to do things with these bikes they were never intended to do so i definately can tell the differance goodluck,happy wrenching!

I found the dual disc brake setup much better (and safer) on the road, especially when surprised by inattentive automobile pilots. I converted my '73 Z1-900 to the factory dual disc setup a long time ago. Did the same with my '78 KZ1000.

I found out how much better dual discs are recently when I rebuilt a friend's '77 KZ1000's single disc brake system. I thought the single disc was pathetic!

About twenty years ago I updated my '73 Z1-900 with Z1/KZ900/KZ650 hybrid front forks, drilled four-bolt KZ 197? rotors (4.5 mm thick), and '78 KZ1000 calipers (and now with DP brake pads). I used the thick 7 mm rotors on my '78 KZ1000 but I drilled them too. Found EBC brake pads on this bike to be easy on the rotors -- these EBC pads provide very good braking power (even in the rain) on these vintage braking systems, but the pads can be noisy.

I switched to 15W fork oil instead of 10W fork oil to help control the heavier front ends, by the way.