Disc brake conversion kz650

I recently inherited a kz650 that my dad bought new in 1980. It hasn't been on the road in 15 years or so and needs a lot of work. I noticed the bike has rear drum brakes. I have seen other bikes of similar vintage with a rear disc brake. I'm wondering what parts I would need to make this conversion work. I've found several disc brake rear wheels that would match the front mag wheel for pretty reasonable prices on ebay but I'm not sure what else I need, ie swingarm, axle, adjusters etc. Anyone done this swap before?

Welcome aboard! Converting to rear disk brakes takes a bit of work. The swing arm is set up differently because the torque link, which is different than the one for the drum brake, attaches to the top rather than the bottom. Also, there are some loops welded to the swing arm to hold the brake hose. You also will need to weld a mount onto the frame to attach the rear master cylinder and make some other brake mods. If possible, that mount should be taken from a junk KZ650-C frame. There are other differences that shouldn't be overlooked, such as the right side chain adjuster, axle collars, etc. The easiest way to get all the correct parts is to find a donor KZ650-C bike and take everything at the same time plus take pictures of how / where the master cylinder is attached to the frame. It can be done, but you need to be sure you have all the bits & pieces before you start the work. Ed

The Fr Br has most of the stopping power, so IMHO it isn't worth the trouble to make the conversion unless stuff is a direct swap, such as on a 650-CSR. Or unless you like doing that sort of thing. I only do the easy or necessary stuff. I would install a dual disk Fr Br before doing the Rr.

Drum brake. If you don't make the conversion, replace the Rr brake shoes. The adhesive that binds the linings to the shoes can fail over time - a lining can separate from a shoe & get jammed between the shoe & drum, locking the rear wheel. It happened to me when rolling the bike off the center stand in the driveway. It would be a real drag for it to happen at speed & far from home.

martin_csr wrote: The Fr Br has most of the stopping power, so IMHO it isn't worth the trouble to make the conversion unless stuff is a direct swap (such as on a 650-CSR). Or unless you like doing that sort of thing. I only do the easy &/or necessary stuff. I would install a dual disk Fr Br before doing the Rr.

Drum brake. If you don't make the conversion, replace the Rr brake shoes. The adhesive that binds the linings to the shoes can fail over time - a lining can separate from a shoe & get jammed between the shoe & drum, locking the rear wheel. It happened to me when rolling the bike off the center stand in the driveway. It would be a real drag for it to happen at speed & far from home.

+1

Dual front disks will improve braking, and since 75-80% of braking power is up front that's a good place to start - more bang for your buck. I like my rear disk brake and prefer it over drum, but frankly the cost to switch from drum to disk is disproportionately high compared to the actual improvement in stopping power. Of course, if you have an inexpensive source for the parts it could be a rewarding project. Ed

Thanks for the responses. The rear might have to wait. I was hoping it would mostly be a bolt on affair. What about the front? Just new wheel, caliper and bracket?

For the front you may be able to use the same wheel, but you'll need a rotor, caliper, bracket, splitter, hoses, & master cylinder. Also, you will need to deal with the lower fork legs so you have something to mount the bracket to. Ed

my mistake.