rear disc conversion

I'm changing my rear brakes to disc on my '79 kz650b and I'm at a loss for how to mount the master cylinder to my frame. Obviously I need to weld it, but I don't have a donor frame from which to steal a bracket or take exact measurements of where it needs to go. Could anyone with a stock rear disc give some measurements for where the master cylinder needs to go? I think that the style of master cylinders vary so I'm pretty sure that it's from a 77C (it has the reservoir integrated on the top of it rather than connected by a line). Does anyone have any custom fabrication tips? Also I would be extremely greatful for any pictures of stock and/or custom mountings.

install brake pedal ,rod and mastercylinder on bike and see where it lands on frame tube that will be the general location to mount it.check clearance on battery box and side covers.you can build a mounting bracket off the rear motor mount but youll have to put the mastercylinder on first to make your mount.goodluck,happy wrenching!

I converted my 77 650 to rear disc when I installed a Zephyr swingarm/GPz 900 rear wheel and brake. My frame is powdercoated and I didn´t want to break the coat to weld on a bracket - instead I did what Wireman suggests, fabbed a bracket that attaches to the rear right side engine mount.

In the pic below you can see the mc and bracket (left), the longer bolts I installed to mount the bracket (right - the large nuts are used as spacers), and finally the mc installed (middle). Also had to prolong the mc link with a piece of stainless threaded rod and modify the brake pedal shaft - took a couple of tries to get it right, but it wasn´t too hard.



Post edited by: onkelb, at: 2006/03/15 11:16

Thanks, I really like the idea of not welding to the frame in case I change something again later. By the way, that bracket looks very nicely done, clean and not so obviously custom. Does anyone have any location measurements for the MC that I described?

Hey I am wanting to do the same thing. A few questions:

1) Is that GPZ 900 swingarm any longer than the stock? I actually want to extend the swingarm a bit on my kz650.

2) Also can I just get any spare wheel off of Ebay & put it on a KZ650? What are some things to consider when getting spare rims from different bikes & putting them on the KZ650.

3) I also want to put a mini disc on the front. Any ideas on which will fit or which stock wheels from another bike have the minidisc already & a disc on back (I think 18 or 19 on back & 21 on front).

Thanx!

I have my master cyl mounted right in front of the battery, and the slave cylinder is mounted to my rear engine mount. The master is on an aluminum bar that runs between the frame rails, slightly under the gas tank. I can take some better pics tomorrow if needed.