I finally am getting around to organizing all my photos from when I started this build about two years ago, so I can document what all I screwed up and learned along the way so maybe others can learn from my mistakes. I have champagne dreams on a beer budget and literally none of the proper tools needed for customizing a motorcycle, so this entire venture is an exercise in doing as much as I can with as little as I can for as long as I can until I have pay a professional. This whole project is really like a self taught shop class for me. I am constantly having to research for weeks on how to accomplish the next step as much of this I have never done. So I may have really struggled with things that other folks could whip out in an afternoon in the garage. So bear with me!
I previously did a ground up restoration on a 1990 zr550 and in the in the process I ended up with literally enough spare parts to build a whole other bike. So after seeing lots of guys in Japan grafting on Zephyr400's (Zephyr zr550 in US) swing arms and front ends onto z750gp's and z750fx2's and 3's, I knew what I was going to do with all my spare Zephyr parts. I wanted a kz750e as they were easier to find than an dual shock gpz or a kz750L or kz700 ( plus I didn't want to irreparably alter a rare bike like those.) It took me a long time to find a bike that wasn't to nice to modify or to trashed to bother with.
Eventually I found a 1981 kz750e with 27K miles that was on it second owner. It had been garaged and taken care of all its life until the second owner, who spray bombed it all black, put pods on it and never figured out the jetting, so it was forgotten in the garage. The gas tank was covered in tinny dimples from a failed attempt at cleaning out the inside with large nuts and bolts, and the rear brakes were frozen solid. But it did start and it ran even though the petcock was fashmoganed and the carbs gushed gas as soon as the engine stopped. So this one was perfect for me to start with.
The day I brought it home.
I wasted no time in beginning to test fit the zr550 parts on the kz just to see how easy or hard this was all going to be. And was pleasantly surprised to find the swing arm fit between the frame bosses with millimeters to spare and the zr550 front end bolted up almost as if it was designed for it, even using the incorrect kz bearings.
So far so good!
Now that I knew that the Zephyr suspension bits were going to work, I made a list of things I wanted to accomplish. I had one and a half entire zr550 parts bikes I could use and the internet to find the rest.
I will skip forward to this past winter when I mocked up all the parts I had amassed to see how and if it would all work together. All the powder coating, suspension work and wiring had been completed at this point, but I never had the engine and the carbs and the gas tank in the same place at the same time, so I was hoping it all was going to fit. And thank God it did.
At the time of writing this, the motor is apart and I just finished painting all the engine pieces...so now it will all have to be sent off to the machine shop for the cylinder boring and valve job.
I ended up with:
1. kz750 frame and motor
2. zr550 front suspension, front and rear brakes, handlebars, headlight, swing arm and wheels
3. zr550 entire wiring harness including ECU, Ignition pickup, coils, fuse block, regulator....the entire thing.
4. zr550 speedo and tach and switchgear
5. zr750 (zephyr) cvk32 carbs and intake manifolds
6. zr750 ignition timing rotor
7. 810 piston kit
8. 1984 gpz750 cams
9. zr-7 sprag style starter clutch and secondary shaft
10. zr-7 high capacity oil pump
11. zr-7 oil sump with oil cooler ports
12. zr550 oil cooler and lines
13. 1984 gpz550 6-speed transmission
14. cheap ebay rear shocks until I can find something affordable and worth using.
15. Kerker exhaust
16. kz1000e (shaftdrive) gas tank
17. zx600d rearsets
I will now try to work my way through illustrating all the steps in between and document reassembling the engine when life stops getting in the way.
Once I had the entire bike stripped down to the frame, I moved into the basement as the Minnesota winter had started and it was to cold to work in the garage. I first started by trying to level the frame relative to the earth and then started trying to determine if the frame was bent or if anything was wonky. After measuring and remeasuring, everything checked out straight, so I moved onto properly fitting the swing arm.
The first issue is that the zr550 uses a 17mm pivot bolt on the swing arm and the kz750 uses a 16mm. I had no confidence that I could drill the frame holes out to 17mm dead-on straight, but I found a member here that had done a zr550 swing arm swap and had found an elegant solution to make it work.
He found that Suzuki swing arm bushings had the correct OD and the 16mm ID that would make it possible to use the kz750 pivot bolt. All that needed to be done is to cut down the zr550 sleeve to fit in between the Suzuki races as a spacer. I ended up cutting down the kz750 sleeve so it was 16mm all the way through and there would be no slop in the ID. Having no lathe, I took it to a machinist, and it took him all of 5 minutes to cut down the kz750 sleeve to 160mm and I was on my way.
Now that I had the swing arm pivot sorted, when I bolted it up to the frame, the swing arm fit inside the frame bosses with about a 1MM clearance between the frame bosses and the pivot sleeve. But I would need to make room for thrust washers on either side of the swing arm pivots to keep the swing arm from sliding back and forth on the inner sleeve. So I took a file and filed down each frame boss until I had (after a lot of trial and error) 2.5mm of clearance on both sides. I took the swing arm caps from the kz750 swing arm and made them into my thrust washers. The caps are 1.5mm thick which gave me 1mm of "slop" on either side to shim the swing arm if I needed. (and I would later find that I definitely need to shim it.)
Suzuki OEM # 61251-49000 bearing races and kz750 sleeve cut down to 160mm for a total length of 230mm. Thrust washers at the ends.
Before I knew better, I spent an insane amount of time filing the frame and spacing the swing arm until I had the wheel in the perfect center of the frame. Only to find out later that the front and back wheels can be offset, and in fact some bikes come from the factory that way in order to facilitate chain alignment. But a year or so down the road I would find that all that work would pay off, as I will need to shift the swing arm over 1mm in order for my chain and sprockets to line up. Shwew!
The front triple tree and top clamp fit perfectly in the frame, and all that was needed was a new bearing conversion kit from All Balls Racing.
The steering stops were not going to work and had to be modified. Of the three zr550 triple tree's I had, all of them had bent steering stops, So I decided they must not be strong enough and so I cut them off and began devising a solution that would work a lot like the kz750 steering stop that is integrated on the frame. I took some scraps of 1/4" steel and cut and filed out two stops that would be welded to the tree. I just needed to measure it all up with the forks and the gas tank, so I knew I had the proper position of the stops before I had them welded on. But I need to decide what gas tank I was going to use......
As for rebuilding the engine......
I have collected all the parts I will need (except my rod bearings, which are on back order), had the engine parts soda blasted, painted all the parts, and will be dropping off the cylinders and head at the machinist this week. I have already done the modifications to the 6-speed transmission and the clutch to make it all fit. (thats another post) I just need my rod bearings to arrive and then I can start assembling the bottom end while I wait for the machinist to finish the valve job and piston bores. (also another post....hopefully)
For the gas tank I was planning on somehow taking the dimples out of the factory one and that would be that. It was most rust free and didn’t have any dents.
But one day as was wandering around the local motorcycle salvage yard, I saw what at the time I believed to be a kz1000 MKII gas tank lying on the ground. It was really rough and full of rust, so I took a picture and when I got home I researched it as a possible “replacement” for my stock tank. I really love the look and of the MKII’s and the kz750e already has the same style tail piece and tail light, so I liked to idea of making mine a MKII "clone". Soon I realized it was not a MKII but a kz1000e shaft drive tank that looks like a MKII tank but is different in several ways.
The shaft drive tank has a different profile that hugs the frame underneath, (that supposedly ads extra capacity) the mounting ears are in a completely different spot, and they are shorter than the MKII tank. (again…supposedly...I have never seen a picture of them sitting side by side)
On my next trip back to the salvage yard, the tank was still in the same spot on the ground and covered with snow. So I found the one kz750e in the yard and set the kz1000 tank down on the frame and it almost fit like it belonged there.
So I found a kz1000e tank online that was in better shape and virtually no rust inside. So after days of talking myself into it, I decided to buy it and see if I could make it work.
When it arrived, it was clear that to start I had to cut off the original mounting tabs to even do a precise fitment. So crossing the point of no return, I cut off the tabs and laid a towel over the frame as a spacer, put the factory rubber spacer on and set it on the frame and it fit perfectly. Even the cutouts in the bottom of the tank for the coils were in exactly the right spot.
I measured the height of the old tank against the new one and spent days and days readjusting the tank into what I hoped was the right spot and then drilled a hole through both sides of the frame gusset plate right above and behind the factory gas tank mounts. I cut and pressed a steel rod through the holes and those became the new mounting perches for the rubber fuel tank mounts. The factory tank mounts did rub on the kz1000 tank, and instead of cutting them off, I decided to leave them just in case I ever decided to go bad to the stock tank. So I just shortened them enough so they no longer hit the tank.
After it was welded on.
I needed to fabricate a rear tank mount, so I then took a strip of steel and bent it to the rough angle and hot glued it onto the remains of the stock mount on the bottom of the tank, so I could correctly position it to the factory tank mounting plate. It took several tries of hot glueing to get the angle of the bend just right and to get the mounting hole drilled in exactly the right spot.
Once the rear mount was finished, I knew I needed a professional welder to weld the front mount to the frame, and to weld the rear mount to the super thin gas tank. Because I only have a cheap flux core mig welder that is only used when I absolutely-need-to-stick-two-pieces-of-metal-together, I thankfully was able to find a local welder that was good and his prices were reasonable.
Now that the tank was permanently positioned, I was able to reattach the front end and correctly align the steering stops and forks with the kz1000 tank and then I was off to the welder again to make that permanent as well.
It turned out pretty good with only a small weird gap between the seat and the tank.
Thats funny you say that, as years ago I was googling z750fx and z750gp and I found a japanese site selling a z750fx-III that is modified with Zephyr400 (Zephyr zr550 over here) and thats what gave me the idea to start this project.
There are a lot of cool Japanese web pages and blogs for kz's as long as you have google translate to help read the pages. But if not, there are lots of cool bike pictures.
z750fx1 ---- small bore kz1000 mkII
z750fx2 ---- kz750e
z750fx3 ---- kz750e with a gpz style tank
z750gp ---- gpz750r1
Next on the list was the rearsets. I couldn’t find any that I either liked, or could afford. The ones I liked most was when someone used later model Kawasaki or Suzuki rearsets and grafted them onto their bike. So I went to the salvage yard and started looking around to see if I could find what I wanted. I eventually found a ’91 zx600d that had ones that I kinda liked and they were in great condition.
I knew that I didn’t want to just weld on some nuts onto the frame to bolt them to, but would rather devise a bracket that would bolt into the holes for the factory foot pegs and then I could bolt the rearsets to those. I found this decision to be the harder and more costly route.
First the factory foot pegs bolt onto studs that are screwed into the frame. But the studs are stepped, so the initial hole in the frame is 10mm then goes down to 8mm threads. So I had to first find 10mm OD bushings with an 8mm ID just to press into the frame holes so my bracket could be solidly bolted to the frame without worry of the bolt being unsupported.
Once I figured that out, I then started by making plywood templates of the bracket with varying degrees of angles so I could get the tilt of the rearsets just right. After about 4 tries I finally got the angle just right and then measured for the spacers that I would need to offset the bracket from the frame so It would clear the swing arm pivot bolt.
ThenI had to make a CAD file for the machinist, so I took a week to relearn AutoCad (It had been 15 years) to the point I could draw up the bracket and spacers so I could have those made up out of 3/8 steel plate and aluminum.
This is one of those things I simply do not have the tools to do, and they need to be dead on, which I knew I couldn’t do with just a hacksaw and a file. But you have to pay for quality work, and pay I did.
I ended up stripping the paint off the rearsets and polishing the aluminum. The rubber footpegs were replaced with ebay ones and the hardware I had re-zinc plated yellow just as it was from the factory. The brackets I had powder coated along with the frame. The zx600d shift linkage was way to long, but thankfully the shift rod from the zr550 is the perfect length.
In the end they cost as much, if not more than new ones, but they turned out exactly like I wanted. They may not be everybody’s cup of tea but I am very happy with my results.