Fork lower length, help deciphering fitment

I've noticed as a I look at pictures of various KZ's, late 70's-early 80's, that there seems to be two different length fork lowers. Where it is noticeable is the spacing between the fender mount and the top of the fork lower. There seems to be no rhyme or reason which bikes get which. You'll see pics of the same year/model bike with either of the two. My 1980 KZ550 has the shorter lowers, I'd prefer the longer version, but not sure how compatible they all are.
Is there any definitive information regarding this?
below are a couple part numbers, part numbers vary year to year as well.
Any info would be greatly appreciated!

1980 KZ550
44006-1018


1982 KZ650
44006-1058

These two pictures are both said to be for a 1980 KZ550. You can clearly see the difference in length above the fender mount.

These are a set of '82 KZ650 lowers I can get. I also like that they don't have the brake mount on the right fork.
Just wondering if these will be a direct swap on my '80 KZ550 forks?

Are those eebbaayy photos?
My guess is the first set is from a KZ750H Ltd. Or maybe a 81 550 GPz. just a guess.
GPz forks should be black. clues = leading axle forks w dual disk Fr brake.

martin_csr wrote: Are those eebbaayy photos?
My guess is the first set is from a KZ750H Ltd. Or maybe a 81 550 GPz. just a guess.
GPz forks should be black. clues = leading axle forks w dual disk Fr brake.

82 650-CSR. They should fit into your triple tree as the fork tubes are 36mm & the front axle is the same. This isn't quite the same thing, but I put 1980 550 Ltd wheels on my 81 650-CSR --- they were a direct swap, very easy. All I needed were the wheels & Fr brake disk. every thing else swapped. This indicates that the 550 disk & caliper are oriented the same as the csr & the fork width is probably the same. The 81 csr forks are 35-1/8" L (tape measure hooked on the fork caps below the air valve) & the lowers are 16.5" L (dust boots moved out of the way for measuring).

My lowers are measuring 14", so yeah, the longer ones are about 2.5" longer. The Dual brake mounts don't seem to make much of a difference either, some have single, some have double. Mine has double even though I only have a single front brake.

Some (all?) dual disk rotors are smaller in diameter than the single disk, so the calipers are located lower down on the forks. I know for sure that the 750H Ltd forks are different than the 650-csr to accommodate the smaller disks.

My drilled disks are the same diameter as the solid ones.
Steve

I went ahead and bought the set from the '82 KZ650, I got them for $20 so figured if they don't fit I'm not out much. Should be here in a few days. I'll post an update.

caliper spacing is different.
oh well.

carwash wrote: caliper spacing is different.
oh well.

That may be the difference the later bikes had the rotors with 7 bolts holding them to the wheel those rotors are 10.25" in diameter the earlier ones bolted to the hub with 4 bolts are bigger 11 3/4"