1980 KZ650F1 REAR DISC CONVERSION

I JUST BOUGHT A 1980 KZ65. IT HAS FRONT DISC BRAKES AND DRUM BRAKES IN THE REAR. IS IT POSSIBLE TO CONVERT MY BIKE TO REAR DISC BRAKES?

Sure, but some parts and work is involved. I also have a '80 F1 and would like to do the same thing. I picked up a '78 B2 (local and free!) with triple disc and got to looking at it. You have to swap out the swing arm (or cut off tab for caliper torque rod mounting from other swing arm and weld to yours) the rim (after looking at both, our rim will not work with disc setup) and you have to weld master cylinder bracket to frame. Plus, I didn't like the style of rim used vs mine. Not a hard thing to do but some work involved. You can ebay all parts or easier would be to locate cheap donor bike as I did.

Wouldn't a B model have spoked wheels with a drum rear brake too?



Welcome BUZZSAW.
Bluemeanie is right though, swap on parts from a model that has a rear disk brake.
C models have an 18" rear wheel, and D models a 16" rear.

Not only is it possible, it's a fairly simple swap providing all the donor parts (rear wheel assy, swingarm and pivot bolt, rear master cylinder/caliper) are there and in decent shape.

I did the swap on my '78 KZ650-B2 (spoke wheels, single disc front / drum rear brakes) a few years ago, and am very happy with it.
I cut the rear master cylinder bracket off of the donor bike frame and welded it to my frame (I ended up giving the donor bikes frame to another KZr member), but you could always fab a bracket up that will work.

Thank you for the quick responses! I have access to top quality fabrication so creating mounts etc. is not a problem. However, I was hoping that the basic components from a "C" model would swap over. It sounds like they will. My only confusion is whether or not I will be able to retain a mag style wheel or be forced to go to spokes? Also, big question!!! What is largest rubber I can put on the stock wheels and still fit the swing arm and chassis???

BUZZSAW wrote:

Thank you for the quick responses! I have access to top quality fabrication so creating mounts etc. is not a problem. However, I was hoping that the basic components from a "C" model would swap over. It sounds like they will. My only confusion is whether or not I will be able to retain a mag style wheel or be forced to go to spokes? Also, big question!!! What is largest rubber I can put on the stock wheels and still fit the swing arm and chassis???

You can have a mag wheel with the rear disc, just not your mag wheel. You need to use a mag wheel that came with rear disc such as my donor bike. My donor bike has a 130 (110 stock) tire on it and fits but not much room for more.

"Wouldn't a B model have spoked wheels with a drum rear brake too?" You might be right Rob, I never really determined what model my 1978 donor bike is!

One other issue, not a big one, but the early triple disc 650 C wheels were tube-type. You may want to stick to tubeless if that's what you have in the front, just for consistency.

The tube-type wheels look very similar to tubeless wheels, but the tube-type don't have the outer lip like the tubeless do, and the tube-type have two rim-lock bolts coming through the rim.

This is all really helpful info!!! Thank you!!! So I guess I need to start looking for a donor bike with the triple disc set up and mag wheels. I love the 130 size rubber!!! What is the hot set up for rear shocks? Any good after market choices?

Since fabrication won't be a problem, you might be able to use a swing-arm/rear-brake setup from a 750-4. They use the same swing arm shaft & sleeve as the 650s, and have tubeless wheels. Just a thought....

NICE!!!

It was just a thought... I have no idea how it would work on your frame. The 80s frames are different than yours. In particular your bike has a muffler stay built into the frame, whereas the newer bikes have a stay that's bolted on & it provides mounting points for some of the disk brake stuff.