front rotor size 1977 kz 650 ?

im confused :S is the 9 rivets a 1000 and the eight rivets a 650 ? the 8 rivets being smaller ? or is it just a year of manufacture thing and they are different in size every couple years or both ? anyhow , the 9 rivet i have is close to 11 inches across edge to edge, what i need is one thats about 10 or so . wireman , could you measure the 650 front end from center of axle to the deepest part of caliper casting ? thats where the rotor i have is hitting , also could you measure from center of axle to the center of the first caliper bolt hole in the leg ? this would help a ton !!! thanx again for your help . ive been trying to finish bike for a little over a year . lotta work , but worth it

Id be willing to bet the 8 rivet version is for 650,The wife took her van to work today with front end parts laying in back.
I can measure the center of axle hole to center of caliper mounting lugs when she gets home to see if its same as yours.
I pulled it off a 650 way back when because I like to use the shorter forklegs on my bikes.
It doesn't bother me so much that some kid snagged the wheel off of it,i did plenty of scavenging myself as a kid! :laugh:
Its the fact the little bastard or 's broke one of the fender mounting lugs off from a forkleg getting in a hurry to grab the damn wheel,I guess Ill be welding that back on!

The eight rivet rotor is 5 1/2" (or really close to that) from center of axle to the edge of the rotor while the nine rivet rotor on my KZ900 is 5 7/8". I have a pair of 650 rotors, a pair of Z1R rotors, a KZ900, and an H2 rotor and you are right, the larger rotors have one more rivet. The 650 rotor has eight.

The calipers are identical between the 900, 1000, and 650 but the mounting point on the 650 fork legs are further down due to smaller rotors.
Edit: I need to read more... I'll measure some forks since I only have to walk a few feet to do so.

Okay, I measured diagonally from the center of the axle to the center of the lower caliper bolt.
My KZ650SR forks are spaced at roughly 2 7/8". Kind of hard to be exact without an axle.
my KZ900 forks are at 3 1/8"

Keep in mind that there were two 77 650 models, the B1 and the C1 - the B1 has spoke wheels and a single front disc, the C1 has cast wheels and dual front discs.

A B1 disc has 9 rivets and is 290 mm / 11.417" across - the B1 fork measures 70 mm / 2.75" from the center of the axle to the center of the lower caliper mounting bolt.

James, looking at your fork lowers, are the caliper mounts and fender stay mounts on opposite sides of the fork tubes or are they on the same side?

ok fellas , off work early :woohoo: let me just say thanx a million
just took measure of axle to caliper bolt hole , 2 7/8 not 3 1/8 , so i do have 650 forks
measured rotor , 11 7/8 or 11 5/8 across, 9 rivets , too big :pinch:
real bummer , this one looks great , and wireman this one came on a nice spoke rim , thats why i got it.
thanks for goin to look in the barn , pretty cool of you
and same to you crazyduck ! anyhow , if anybody has a 8 rivet 650 rotor thats approximately 10 1/2 to 11 inch
across edge to edge , let me know . im in indiana :woohoo:

OnkelB wrote: Keep in mind that there were two 77 650 models, the B1 and the C1 - the B1 has spoke wheels and a single front disc, the C1 has cast wheels and dual front discs.

A B1 disc has 9 rivets and is 290 mm / 11.417" across - the B1 fork measures 70 mm / 2.75" from the center of the axle to the center of the lower caliper mounting bolt.

James, looking at your fork lowers, are the caliper mounts and fender stay mounts on opposite sides of the fork tubes or are they on the same side?

looks like i have B1 forks , my rotor has 9 rivets and doesnt fit , about 1/2 to big so , i dont care about how many rivets just the right size which i think is around 11 inch or a little less . thanks for the info though . ill go check fender stays

If you have B1 forks the caliper mounts will be opposite the fender stay mounts (fender stay mounts behind the leg, caliper mounts in front), if so the large rotor should fit.

If the caliper mounts and fender stay mount are on the same side you have C1 (or later model) forks - C1 and other dual disc models have smaller discs so the caliper mounts are sitting lower on the fork leg, which would explain why the large disc won't fit.

well looks like C1 , fender stays on same side , do i have to run dual disk ? i know performance wouldnt be the same , but will it damage something ? this bike will be for easy cruzin , no racing or continual hard breaking . i thought it was optional even though i saw the other caliper mount on the right side . thanks again

Alright heres the forks I brought back,you can see the broken fender lug on right leg. :sick:

Alright heres the forks I brought back,you can see the broken fender lug on right leg. :sick:

wireman , thanx for the pictures those are the same forks i have . thats impressive welding skill to be able to repair an aluminum fender lug , wow . im gonna be on the lookout for the smaller rotor now. thanks to all members that helped school me on this subject. once again this forum and its members never ceases to amaze me , KZR kicks butt , thanks

indianajames