kz750e Resto-Mod

i would just like to let you know that you are a terrible influence.

I had pretty much put the 6 spd idea aside, far less than back burner.

With that being said, i was getting ready for work this week, minding my own business, and the ebay app on my phone sent a notice. One of the gear sets that I was watching had been reduced to a super stupid low price. It was a "best offer" listing, "Hmm," I said to myself, "that's interesting". About half an hour later I couldn't stand it any longer so I made a super stupid, low ball, less than shipping, offer on the already super stupid low price. Approximately an hour later, after I had arrived at work and was getting started with the day I got an alert saying the offer had been accepted. Well shit! Now I have a gear set on the way for less than $25 shipped. That's Not just the gears but the drum and forks too.

Now I have to check to see if that crankcase is still available and find the rest of the fixings for building a Franken-engine.

GPzMOD750- Hopefully my transmission swap right-up will come in helpful when you are ready to do yours. Or at least you can learn what not to do...only time will tell.

While on vacation in Belgium, France and Germany, I saw only one "vintage" Kawasaki. We were at the local village pub in Lombise, Belgium when this beauty pulled up. I speak virtually no French to compliment the bikes owner, so I just gave him a thumbs up as he walked by.





But while I was away, my connecting rod bearings and base gasket showed up in the mail. So now I have no excuse not to start assembling the bottom end while my cylinder head is still at the machinist.

Thanks for all the info!! Anxiously awaiting this transmission writeup.

I bought a Kz700 and got it minimally road worthy to ride back and fourth to class. It's my first "old" bike and absolutely fell in love... Now I'm contemplating an 810 kit and 6th gear.

When you do the trans writeup, can you mention what parts were needed from the 550? Im starting to collect zr transmission parts and want to try to have everything I need to do the swap before I start.

So I have finally found the time to assemble my bottom end now that my connecting rod bearings showed up. So that means I finally got to fully assemble the 6-speed transmission and seal the cases so its time to document what I did.

First what I needed for the swap:

1. zr/kz/gpz550 6-speed transmission. (They all have the same gear ratios. I had two ’84 gpz550 transmissions in my basement so that is the only reason I used that particular model. The zr550 has a 10mm longer output shaft in case you have a really wide rear tire.)
2. Shift drum and selector forks and rod from corresponding 6-speed transmission.
3. 550 style sprocket and splined retaining ring and bolts. ( I used a 530 17-Tooth 13mm offset sprocket. I have a non stock swingarm and rear wheel that required the offset sprocket)












What I also needed but can be reused from the 750:

1. Transmission bearing cap with clutch pushrod port. ( The gpz transmission I used is not a pushrod clutch, so the bearing cap was the wrong style. If you are doing this on a later model 750 with the lever type clutch release mechanism, then this not needed.)
2. Gear selector linkage.
3. Transmission cover.
4. Clutch assembly
5. Neutral spring and plunger
6. Shift drum alignment bolt

The transmission is simply installed in place just like the 750 transmission, only making sure that you have the correct style bearing cap installed for your particular clutch release type.









The 550 shift drum installs in exactly the same way as the original, BUT TAKE NOTE OF THE ORIENTATION OF THE SHIFT FORKS! The 550 shift forks install facing different directions from the 750 ones, so get a 550 manual to make sure you are installing the forks properly!!





Assemble the upper and lower case halves (making sure the shift drum is in the neutral position) and make sure that the transmission spins freely. There are shims that can be swapped out on the input shaft in the event that the transmission binds when the case is bolted together. The directions for this are in the service manual.
I luckily had no issues.
Install the gear shift mechanism to the shift drum. I then spun the input shaft with a cordless drill so I could get past the neutral lock out and made sure I could select all six gears before going any further.





Install the transmission cover as normal. On the kz750e I installed this on, the neutral indicator lamp switch and contact on the shift drum lined up perfectly and no modifications were needed to make it work. ( It is possible that other models with out the push rod clutch may need to have the shift drum contact plate unscrewed and re-indexed to align with the neutral switch on the transmission cover. Again…Possibly.)





The clutch for the 550 transmissions are much smaller and as a result the input shafts are shorter and there aren’t enough threads to fully bolt on the 750 clutch hub.
The 550 clutches will work but they have a totally different primary gear ratio (2.934) than the 750 (2.55)
So different that it is would negate and benefits of swapping to a 6-speed.






The nut is 3mm short from fully threading onto the input shaft. So I had a machinist remove 3mm from the inside of the hub. There was a washer originally under the clutch nut, so for some reason I got it into my head I should also make room for a washer, so I had the machinist remove another 2mm to make room for a 47x16x2mm stainless washer for a total of 5mm of material removed from the inside of the hub. I used such a wide washer as I didn’t want to recess the washer and nut into a hole that I couldn’t get an impact socket into.
If I was to do this again, I would not make room for a washer and only remove the 3mm and not use a washer at all.
I then bolted the clutch inner and outer hub onto the input shaft using loctite. Only time will tell if this holds up to the rigors of normal usage.


Note that nut is not fully able to thread on shaft.













The only issue I had with my sprocket is that the offset sprocket had a much wider splined area and it would not fit onto the output shaft. There is a collar that is on the shaft that the transmission cover seal rides on that is taking up to much space.
On the 750 transmissions this collar is held on by the sprocket which is bolted in place and once the sprocket is removed, the collar slides right off. But the 550 collar is pressed in place as the sprocket is held on by a splined collar that allows the sprocket to “float” on the output shaft. The 550 collar is designed to be removed by pulling off the outer bearing. Instead of doing this, I wedged the collar away from the bearing with a jewelers screwdriver just enough that I could fit a bearing puller on the collar and pull it off. I then had to have 3mm of the collar machined off to make room for the new sprocket and give it room to float. Then I pressed it back on and it sits just flush with the outer edge of the seal.









Note gap between sprocket and cover




When I was researching this swap I got on gearingcommander.com and started running all the numbers to see if what kind of RPM’s and speed benefits could be made.
This is the factory kz750e gearing stats:





This is what ended up using to keep close to the factory gearing yet adding a usable 6th gear:

1. 6- speed transmission
2. 530 pitch chain
3. 750 clutch with 2.55 primary ratio
4. 17 tooth front sprocket
5. 39 tooth rear sprocket
6. 140/70-18 rear tire

For a final result of:









I need to adjust chain slack yet.

So I also had a ton of slop in my clutch basket so after much research I decided to try and replace the rubber dampers in my clutch basket. The dampers are not designed to be replaced by Kawasaki so they don’t sell the dampers separately. So I first bought new Viton rubber reproduction dampers from a guy on 750turbo.com (There was a pdf of step-by-step instructions on their site on how to do this mod, but I don’t know how to attach it.)


First I needed to drill the rivets out on the back of the clutch basket.







It is very common to find broken of crumbling dampers, but none of mine were broken, just shrunken and rock hard.

Old and new dampers compared.




The cover can be welded on, or screwed on. Because I don’t have a very good welder I chose to screw my cover back on, as the cover is very thin and I would have ended up warping the crap out of it or destroying it all together. This required pressing out the old rivets (much easier said than done) and tapping new threads in the rivet hols. Because there is so little clearance between the back of the clutch basket and the engine case, I had to source ultra low head bolts to screw the cover back on. There is only space for 1.5mm of weld or bolt head to stick out from the cover.
I used loctite and staked the bolts to the basket in an effort to keep the bolts from backing out and destroying my case.







Bolt heads are exactly 1.5mm high

wow you're doing some cool stuff here. great write up on the 6 speed swap.

I'll print, scan and copy as a pic so I can post the PDF's.
Steve

Very cool, wish I could do that. Can you put a washer behind the sprocket so it won't want to walk around?
Steve

swest: The spockets are designed to float or walk around. On my zr550 there is a 7-10mm gap between the sprocket and the collar. I would have imagined that the sprocket would wallow or wear the splines on the output shaft, but they don't. I have seen pictures (on a japanese blog) of people trying to use circlips to keep the custom sprockets on instead of a splined keeper and it damaged the groove in the shaft. Very weird how a circlip would eat the shaft but not the keeper of a wandering sprocket.

Thanks man. I can't wait to try it out.

I took swest's suggestion and took screen shots of the clutch rebuild pdf so I could post them.

The instructions are not mine and were created by someone over at www.750turbo.com/
I followed the directions exactly, except I used different bolts.

I'd feel uncomfortable with depending on just the splined washer and bolts. On mine the sprocket is torqued to the collar with a bend over washer. Even with that, the nut has backed off against the sprocket cover. Luckily the shaft is threaded so the nut tightens kinda when it hits. The later 1000's have a bolt that can come out. :blink:
Steve