we want to see your pictures, kz650 with 18" mags

I think you will absolutely notice a handling improvement.

This is why I bought it.
I was talking to a mechanic at the Kawi dealer about tire sizes and handling, mainly the rear. I was asking if a 120 rear would handle better than the 130 I presently have. One person I know of went back to the 120 and personally liked it better. Ma Kaw engineers thought so as well.
The mechanic and I also talked about front tire possabilities.

Then the mechanic said something to the effect that if I wanted even better handling, find myself a '78 Z1R 18" front wheel. It's a dirrect swap as the brake rotors will just swap over from my 650. Off I go and find one.

The mechanic races 650/750s in Vintage Racing, so I figure he must know a little about handling.
I gave him one of my 650 motors, and he is building me a braced swingarm, stock length. Should be ready soon, I hope.

During my search though, another person mentioned Ma Kaw swiched the '80 Z1R to a 19" front wheel because of stability problems with the '78's 18" !!
Any truth to this issue?

Bad Kaw, have you had any issues that you know of with stability of the '78 Z1R.
I read where you said in another post about it having a squirrly feeling powering out of corners, or something like that?

I didn't build her my brother did but here she is with Lesters.

rstnick wrote:

I think you will absolutely notice a handling improvement.

...During my search though, another person mentioned Ma Kaw swiched the '80 Z1R to a 19" front wheel because of stability problems with the '78's 18" !!
Any truth to this issue?

Bad Kaw, have you had any issues that you know of with stability of the '78 Z1R.
I read where you said in another post about it having a squirrly feeling powering out of corners, or something like that?

Yeah, I had two ’78 Z1Rs, both of them liked to dance around in the corners. The higher the speed of the corner, the worse it was. Neither of them were a problem in the slower corners. I don’t suspect the 18” front to be the problem so much as I suspect a confluence of several things:

> The 18” front wheel is admittedly narrow at 2.15 inches, so the contact patch is going to be relatively narrow (although not more narrow than the 19”).

> The frame is basically a Z-1 which was available in late 1972 (as a 1973 release)…and remember the “Project New York Steak” was ready to be released as a 750 when Honda released the very first CB750 (sohc) in ’69. So, in short, the frame is basically a design from the end of the 60s. :ohmy:

> The stock rear shocks were total crap and both my Z1Rs had ‘em. Most people don’t know that problems that they perceive to be ‘front end’ issues actually originated in a rear-end suspension problem: shocks, swing-arm bearings, rear wheel bearings, tire pressure, etc…:blink:

> The front fairing was mounted on the forks. The fairing is beautiful and made out of fiberglass…it’s heavy. The wind-force that the fairing deflects has to transfer the energy somewhere, in this case it’s the forks, not the frame. I am very suspect of the fairing b/c I have ridden several high performance Z1Rs and GPz(’81-‘82)/ELRs that exhibited similar weirdness in the handling...and all these bikes had frame-mounted fairings. In each case of a steering damper being added, the instability disappeared. With one particular ELR that I ‘test rode’ it would start to wobble in a straight line once you got above a certain speed (well into triple digits); that bike had an MTC big-block that pulled – obviously – very hard.

> Steering head bearings. Mine were abused, and stock...could have been a contributor, but: the performance Z1Rs/GPz/ELRs that I rode had brand new tapered-roller steering head bearings, yet still squirmed...but not after a steering damper was installed.

Sorry about the dissertation, but here is what I think: your application of the 18” wheel is going to yield benefits, period. I’ll be shocked if you have stability issues, but if you do the cure is a steering damper away. 18”s aren’t the problem, they’re only 1” radially shorter than the stock set up, and it’s not like that difference would send your rake-geometry into the low 20-degree range or anything. I think a lot of little things made both my Z1Rs ‘weird’…and I’ll be finding out this summer (hopefully) as I’m adding a 1260 motor to my ol’ stocker (if I get the head done in time...got a grand to spot me? ) and we all know that more power only makes suspension issues worse.:ohmy: I’ll be frame mounting an FRP fairing, adding inverted suspension, big swingarm, and wide 17”s (all off a ’91 FZR1000) to it.

I’m no Wile E Cyote, super genius; but I’ve seen several high performance Z1Rs (Japanese and Eurpean), they all had their fairings mounted to the frame, they all had steering dampers, some had inverted forks, all had either 17”s or 18”s. One was even a top speed record holder of some sort out of Japan. I think your 18” is only going to produce good results for you especially considering your particular application.
Keep posting and let us know what you think. I suspect you’re going to be pleased.

-KR

I am very suspect of the fairing b/c I have ridden several high performance Z1Rs and GPz(’81-‘82)/ELRs that exhibited similar weirdness in the handling...and all these bikes had frame-mounted fairings.

Do you not mean to say they had fork mounted fairings?

rstnick wrote:

I am very suspect of the fairing b/c I have ridden several high performance Z1Rs and GPz(’81-‘82)/ELRs that exhibited similar weirdness in the handling...and all these bikes had frame-mounted fairings.

Do you not mean to say they had fork mounted fairings?

Yes, I did. You caught me. Forgive me, I had to write that response twice; my 2yr old boy was practicing his 'take down' technique on his 3.5yr old sister and she gave him a little love right back...I need a black-and-white striped shirt and a whistle around this house! :silly:

-KR

BTW: one of the Z1Rs had a 1260 with n.o.s. and a 4.5" over arm. It stood straight up on me when I hit the button shifting into 3rd gear. The frame hadn't been raked (yet!) and when it came down the thing was going I-don't-know-how-fast and it went into a head-shaker that launched me out of the seat, I kept a hold of the bars and by the grace of God I landed back on the seat and just coasted thru the traps...soiled trou and all.
-KR
PS> That was a fun bike...off the juice.

Finally getting around to swapping on the 18" Z1R front wheel onto my 650.



Got the rotors swapped over from my 19" wheel, the new tires (Bridgestone BT45s) are at my work. Just waiting on new tubes and Spring to take the first ride.
Pictures to come with the wheels installed...

18" on left, 19" on right:



With 19' front and some photoshop color change:

krcrawford29 wrote:

Hi eslaterb, I might be interested in swapping. Do you know what the widest rear tire is we can fit on the 18" rim without having fitment issues?

Depending on tire brand, I believe a 130 is about as wide as you can go?

Put on a 17" front

Got out for my first ride this season, with the 18" front on.
Roads are still sandy in places, and I have new tires on so I took it easy.
Felt good overall.
Got down to Lake Simcoe and saw some people still ice fishing:









.

Well as soon as it warms up I'll be very interested in your feedback on the 18".
-KR

It's been hot here lately.
Almost too hot to ride.

I have been out a fair bit though, and am loving the new tires and 18" wheels.
I was a bit concerned about reported wobbles with the 18" front wheel on Z1Rs (that's why they switched to 19" front on the '80 Z1R), but so far have not had any problems myself, and I have taken her up to high speeds.
Taking corners feels really good now. I can easily use my body to lean the bike over, but since my last rear tire was getting a little bit of a flat spot in the middle, having a new rounded profile sure makes handling feel different.


Early in the season:


Out at a local meet: