My Gpx/Ninja 750r modification started around Feb. 2010 when I sold my stock exhaust for silly money to a guy who really need it and I knew I want to change my exhaust just don’t know which one or any that is still available for my 20+ year old bike so my bike sit in the garage without a exhaust for weeks while I research for parts and it just grow from there. I search the web and found many enthusiasts around the world from France, Germany and Japan that done amazing mods to their 750r but none in the US where I’m at. The Ninja 750r which won Bike of the Year in 87 and beat Honda’s VFR750 at their own game is now a forgotten keynote in history as Kawasaki did not continued development of a sport touring 750 instead the 750r engine live on in the legendary ZX7 where Scott Russell won the World Superbike in 92 and ZX7 continued in production until 2002.

My previous mods to my 750r was retrofit a 88-90 ZX10 17x3.5” front & 18x4.5” rear wheels to my bike but the handling was not satisfactory to my opinion. The stock 750r have a front axel dia. of 15mm (modern bikes are 25mm) so even with a 17” wheel, the small wheel axel and skinny fork tube of 38mm did not inspired confidence I was hoping for. So my conclusion is that just putting on a 17” wheel with modern rubbers won’t improved the handling much, you need to address all aspects of the front end from axel, wheel and fork diameter.



My concept was the keep the original styling of the 750r which I loved but update the running gear to modern standards like 17” rims better brakes and suspension. I also wanted a subtle mods feel to the bike giving the impression if Kawasaki was to introduce the 750r at 2010, this is what it might look like, a retro modern classic from the 80’s
Parts use for the project are listed:
94-95 ZX9 41mm Up Side Down fork with 25mm Axels
94 ZX7 Top & Bottom Triple Clamp with 750r Stem Swap
92 ZX7 Front wheel 17x3.5” with 94 ZX7 320mm rotors
93-95 ZX7 Rear wheel 17x5.5” with 230mm rotors
92 ZX7 Front brake master cylinder
Heli-bar 52mm diameter Clip-On for 94-97 ZX9
01-02 Suzuki GSXR-1000 K1-K2 Tokico 6 Piston front Calipers
89 ZX7 H1 Rear Brake Caliper and hanger 20mm axel
90-93 ZX11 C Rear shock 12.5” (eye to eye) long
Muzzy Stainless Exhaust Header and 2” Mid-pipe for 87-90 Ninja 750r
SuperTrap Internal Disc Muffler (4.5” diameter can with 2.5” inlet) off a 90 ZX7 model
Custom Frame Sliders

Rear Swing Arm Conversion

88-90 ZX10 Swing arm drafted onto Ninja 750r



1st shock modification was a 02 SV650 rear shock (as shown in picture below) where top & bottom mount was drilled out to 12mm, orginal sv was 10mm.




Rear shock are updated with 91-93 ZX11C rear shock with reservoir. The stock shock is 12.18” long and ZX11 shock is 12.5” long. ZX11 shock top eye mount have to thin down for clearance to fit into 750r shock mount. The 750 top shock mount also have to be grind down on the edge for ZX11 shock to rotate freely.






Both use 20mm Rear Axel but 750 use 17mm pivot axel and ZX10 use 20mm pivot axel, have to enlarge frame mounting hole by drilling it out from 17mm to 20mm. Using two drill bit size to enlarge it slowly, first one is 47/64” (18.6mm) and second bit is 51/64” (20.2mm).




ZX10 Pivot axel is also longer then the 750 so custom shim is made with inside diameter of 20mm and outside diameter of 32mm. and ¼” thick.



ZX10 Swingarm is also wider then the 750 so each side have to be machine down 1/8” to fit the frame. The inside spacer that axel rod slide through also have to be machine down.




Also swap the ZX11shock links to ZX10 swingarm to raised the ride height a little bit. Stock 750 shock link is 6” eye to eye and ZX11 rear shock link is 5-3/4” eye to eye. The shorter the links the higher the rear end, the longer the link the lower the rear bike height.






Next I tackle the frame slider but since the 750r is 20+ years old, there is no way I can buy a kit off the shelf so I have to mix and match to work with the 750r and I don’t want to cut the fairing to fit the slider. I combine 08-09 ZX10r frame slider bracket with 06-08 ZX14 slider spacer and a Targa TL1000 slider to make it work.






Next I move onto the front end of the bike.



At first I tried a 94 ZX7 to fit on bike then I realized the ZX7 fork is 3” too short and I might hit the radiator if I brake too hard so after researching around I find out that of all the Up Side Down fork make by Kawasaki the 94-97 ZX9 forks are the one that is closest to stock fork length.
(Top Pic) 94 ZX7 Fork: 28-1/4” from center of axel to top of fork
(Middle Pic) 94 ZX9 Fork: 30-1/4” from center of axel to top of fork
(Bottom Pic) Stock Ninja 750r fork: 31-1/4” from center of axel to top of fork



After the fork length is decided I have to make a triple clamp that work with the ZX9 forks. I tried the ZX9 triple clamp 52mm and it will not work as it mount the clip-on on top of the triple clamp and it will lower the front end too much. So I decided on 94 ZX7 top & bottom triple clamp 52mm which mount the handlebar below the top triple clamp. Don’t mix and match ZX7 and ZX9 triple clamps as the offset is different, ZX7 has more offset so you’ll get more stability. I have to custom make spacers to swap out the ZX7 steering stem and fit the 750r into it. I also have to make a spacer on the top triple to fit/align 750r stem.







Wheel Modifications

ZX7 & ZX9 forks both use 25mm Axels so there is no problems with the front wheel. The rear wheel is a different matter. Since I’m using the 88-90 ZX10 swingarm the 93-95 ZX7 rear rim uses a 25mm axel but the ZX10 use a 20mm rear axel. I find out basically that all Kawasaki bikes that use eccentric chain adjusters from ZX10, ZX11 and ZRX’s all have 20mm rear axels.



By pure chance I find a 89 ZX7 H1 rear rim on ebay and find out that only 89-90 ZX7’s have 20mm rear axel and from 91-02 all ZX7 switch to 25mm axels. I take out the rear wheel spacer and bearings from the 89 ZX7 and it fit 93-95 ZX7 perfectly, the only difference being the inside diameter of the wheel bearing is 20mm instead of 25mm. You also have to swap over the rear hub bearing so all bearings have 20mm diameter. The 89 ZX7 rear rim and 93 ZX7 rim are different design (later version are lighter and more compact hub) so hubs don’t interchange but the 5 bolt pattern 230mm rear disc do interchange.






Rear Caliper Rebuilt



I’d also change the instrumentation T-10 bulb to LED type and it make a huge difference in terms of brightness.





Finally I have to put on the exhaust system, originally I bought a new old stock full Supertrap system that fit the 1990 ZX7 hoping it would also fit the 87-90 750r since the engine is basically the same. Then after fitting the header, I realized the oil cooler locations and mounting are not the same so it won’t fit. I almost give up, then I luck out on ebay and find a stainless Muzzy header and mid-pipe that is just not available anymore so I grab it and it fit perfectly. Well almost, the Muzzy have a 2” mid pipe and my Supertrap Can has a 2.5” inlet pipe. I called a local exhaust company called AREA P No limits and they are willing to custom make a 2” to 2.5” adapter so I can make the two work.



When I hit the starter button and hear the motor light up after 7 month of hibernation, I’d almost cry, it’s the most beautiful sound you’ll ever hear.

Hi, it's really a very beautifull bike what you have buildt ! Congratulations !!!!

Now a question to the seats ( I have seen three a little different types on your pictures) - I'm very interested to know where
have you bought these , do you have an adress or are these all spezial-produced seats ?

Thanks and good luck with your GPX !!

Jodie

yes frank - you're the best - ist´s a super work!!!

Thanks for the great manual. It will help many people.

HI Jodie,

I have three seats, one original, one made by Corbin and one is a custom solo seat with red covering. As far as I know, there are no more aftermarket seat you can buy and Corbin no longer make their seats also. Your best chance is to buy a used stock seat and modified it like one of my seat or you can search on ebay to see if you can find a Corbin or other MFG seats.

Our bikes are 20+ years old, if you find something new for sale, or rare item like exhaust systems or accessory, grab it.

Cheers
FRank

Hi Fiete,

Your green GPX is also a inspiration for me when researching on modified GPX's. I love to see more pictures of your bike.

Cheers from USA

Frank

Hi when you retro fitted the zx10 front wheel was it a straight forward fit into the gpx forks or did you have to change the wheelbearings in the wheel and did you have to space the gpx brake calipers to make them fit the zx 10 discs? also when you done the whole wheel conversions on the gpx in the project diary did you use the standard gpx gearing on the new wheels or did you have to change the gearing to compensate for the change to 17inch wheels? thanks ? it is an awesome looking gpx and the conversion is amazing ,how did it handle after you had done the conversions ? thanks Scott

Hi Scott, Not been on the site for long time, just move to a new house and remodel and took almost whole last year off on my GPX. I use to fit a 88-90 ZX10 front wheel and its a lot of work as the old ZX10 use a vary unique floating disc mount so you have to machine material off to fit stock 750 rotors. Regarding bearings, the only bearing that I could find that have stock 750 15mm diameter front axel and outside diameter of ZX10 wheels are from Bearingsdirect.com Part# B15-86DU. I don't recommend the 88-90 ZX10 wheel swap as you have to machine the rim and speedo to center the wheels and its heavy.

Gearing wise, I did have to change the front and rear sprocket ratio to better work with 17" rims. Stock is 16/47 ratio I change it to 16/45 then again to 15/45, I'm still searching for the right combo.

Handling wise, at first its a bit heavy to get into turns as GPX has 27 rake and ZX7 has 24 rake angles and changing wheels from 16 to 17" rims and 18 to 17" back did not help with steering. I have to put together a hybrid shock ZX11 D top part with 95 ZX6 bottom and its smaller diameter spring to get it to fit my ZX10 swingarm and increase shock length from 12" to 13-1/4" length to raised the rear end and sharpen the steering which it did.

Hope this helps, Frank

I'll update with my project with you guys, I'm pretty much done with what I can do to a GPX and still love riding it and working on it. I hope to share what I learn from my project bike so it will make your life easier when some of you try to modified yours.

Past year I've been trying to imporved the handling of the bike as I swap the front 16" to a 17" and Rear from 18" to 17" and it just handle vary heavy. Since my 94-97 ZX9 fork are already 1" shorter I don't want to drop the front end anymore so I can only raised the rear with longer shock. At first I try the ZX11 C shock which is 12.5" long (stock is 12") and its still not enough to lighten the steering. I then try to put a ZX11 D shock which is 13.25" long but the spring is big a diameter so it will interfare with swingarm clearance before shock eye will fit. I bought couple ZX6 and ZX7 shock and some are too long and the bottom shock mount width is also too narrow so I decides to use a hybrid shock, I use a 95 ZX6 top part with ZX11 C bottom shock and I transfer the narrower diameter spring from the ZX6 also to provide the clearance to fit the 13.25 shock into my swingarm. It work! A lot of work as I have to machine off some material on the bottom shock mount to allow the spring to fit.



After that I upgrade the carb to a Dynojet jet kit. I'd try stage 3 but the main jet is just too rich, way too much fuel so back down to stage one. Have to raised the needle 1 clik higher then instruction and installed the new springs.







I'd also pick up a Vance & Hines Ignition advancer to more low to mid-range power increase and it only took 15min. to install it.







I'm still trying to fine tune the handling of the bike and might still go for a adjustable offset triple clamp for ZX7's is budget allows but for now I'm justing going to enjoy the bike for what it is and my vision of what a GPX750 could be. I might be a little crazy to spend the kind of work into a GPX 750 givin its a bike most have forgotten or give much credit but to me its the bike of my youth and its hard to put a value on that. Enjoy!

Hello fjyang!

You did really a great job on this bike. It looks very good.

Greating from the Eifel

Thorsten

Love the project...Awesome work...

I have the same motorcycle and would like to know where can I get the flush turn signals.
Please send me a link or part number.

Thanks...

Good job-but the back-seat is to high-it destroys the line of this great build motorcycle.

But that`s all -the rest is wonderfull and touches all senses....great job!!

I'm jealous of the small license plate...
I like the "tech-mods" most and the whole bike is looking very good...
But I must agree, the passenger seat is a little bit too big and round for this slender, rather "edgy" bike...

schubl