85 GPz750 Refresh Project

Thanks Kawi810 And Steve any style that is using gear is cool in my book

Pops likes.

Speaking of front fork springs and progressive ones, if I decide to go that route I would want to make sure I am picking up the right ones. I found these but it says they are for a 1982 GPz 750, is there any difference or are these a-ok or what?

www.partsnmore.com/parts/kawasaki/gpz750...%5Bfitting%5D=custom

Most of the others I've found so far from a quick google power search come from the UK and being in the USA I would rather avoid that since shipping would be a bi-otch. This one says it would fit the GPz 750R, any difference?

kglracing.com/shop/motorbike_parts/shock...0_r_zx750g_1985-1987

Lastly what kind of weight would I want to run for oil, I read that wth progressive springs likely want to go 15W and no air pressure. Can anyone chime in on thoughts for this?

Thanks,
Brett

I got mine on eBay from the company named progressive. $78. They sent them FED EX but I didn't get them. Seems the driver delivered them to the wrong place or kept them himself. I never found out which. I had a package on the same truck from Rock Auto and they got to the bottom of it. I finally got my springs (they thought I was a dead beat) replaced my seals, NOS boots, (mistake), new seals and am running 15W oil. I love em. I installed air caps on mine years ago, (waste of time) and don't use them.
Steve

Thanks Steve appreciate the information and pics that helps! Also good to know that when it comes to the seals and caps NOS is not the right way to go simply due to age of materials there. The 15W and no air is what I had read so good to hear that you are using the same setup with good results.

If I may ask, how did you determine that the eBay seller was selling the correct springs for your KZ650 specifically? There are several springs I can find for GPz750's but many are for Turbo's (E) or the R models or GPz550 etc or different year such as a 1982 GPz 750, its a bit difficult to pin down the right one since I am not smart enough to know what differences if any there would be in the springs.

Most of the information I read regarding these can be found in this article which was a compilation of GPz mods and tips passed around a road racer community. It is a really really slick article with some terrific information in there. About 2/3 of the way down is a section talking about suspension and specifically forks/progressive fork springs and fluid weight etc. Seems according to this that the anti-dive unit when progressive fork springs are installed starts to create a problem when you are reaching the limit of compression on the forks. Thoughts?

members.tripod.com/gpz_rider/technical/FAQ2000.htm

Thanks,
Brett

Mine is a 75 Z1b. It was a 900 until 78. I've read the anti dive feature is done away with and some have posted on here. I haven't done one of those mods but I don't see how progressive springs would cause a problem. Maybe someone else can chime in and sort this out for you. TTYL
Steve

swest wrote: Mine is a 75 Z1b. It was a 900 until 78. I've read the anti dive feature is done away with and some have posted on here. I haven't done one of those mods but I don't see how progressive springs would cause a problem. Maybe someone else can chime in and sort this out for you. TTYL
Steve

Hey Steve,

The reasoning behind my anti-dive and fork spring comment was from an excerpt of that article I posted the link to, this section specifically I believe:

"Antidive on the GPz750 works in the following way: Brake pressure works a piston in the anti dive unit that closes off a fork oil passage way from the forks. This deprives the fork oil from getting at some holes in the damper rod. The result is drastically increased compression damping under braking. The anti dive is not particularly effective on the GPz750. Removing it made a major improvement. Why is it so bad? The increase in compression damping upon braking makes the front end so hard that it has trouble tracking over bumps, especially with the Progressive fork springs installed. I was only using up half my fork travel and the front would slide under hard braking since the weight was not being properly transferred to the front tire. Note that improper fork bushing tolerance makes the anti-dive less effective as oil seeps through the bushings instead of through the damping rod. If your bushings are sloppy, your anti dive may be partially disabled already. "

The article does a great job talking about how to remove it altogether but it really sounds like unless you're pushing this bike near its limits it wouldn't have much if any impact. And honestly I think it would be silly to push a 30+ year old bike anywhere near its limits. I certainly don't know what might magically fail at the worst time due to age plus I have no desire to wreck such an awesome and clean example of this rare bike.

- Brett

Riding comfort. Sometimes designs just don't work as intended. My stock springs were stiff and changing oil made little difference.
Steve

Makes perfect sense and for me riding comfort is very important. I have degenerative muscular and spinal conditions and so have bad hands and bad back. Hence why I am replacing the grips for more comfy ones and a few other small things. I gotta believe that the forks haven't been apart in 30 years since she rolled out of Ma Kawi's factory, so rebuilding them and adding in progressive springs sounds like a good idea and would also help with comfort and stability. We shall see, and will be looking into it more.

Thanks,
Brett

Ok got some more information, some of it a bit conflicting.

Talked to Progressive Spring Co., they said that according to them the 1984 GPz750 progressive springs will not work in the 1985. They suggested one of two things, first was to potentially look at GPz1100 fork springs, and the other was to try to reach out to Kawasaki and see if I can't find out specs for both bikes and years etc and figure it out myself that way.

So, I called Rocky Mountain Kawasaki (dealer)i here in Longmont,CO and talked to one of the old timer parts managers. According to them and the parts list from Kawasaki Industries, the 83', 84' and 85' GPz 750 front springs are all the same exact part numbers in the Kawi system. I think what I am going to do is dig through Partszilla myself and see if I can't confirm with my own eyes that it is the identical fork springs and part numbers for 83'-83' GPz750's.

If anyone has some more information or ideas would absolutely love to hear them!

Thanks,
Brett

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