With a few more small parts delivered today, I could fit the Mikuni RS34 carbs.. which went on no problem, though I will make a small support bracket to help take their weight, as with no air box, they are only supported by the inlet rubbers. Next I fitted the exhaust cylinder head studs, again no problem, followed by the 4 down pipes and 4-1 collector, which also went on the bike with no problems.. However, once fitted, it was soon clear I had yet another problem, a big problem..  The exhaust was made to fit a GPz1100B1, same as the engine in my bike. But the rear wheel and swing arm are obviously wider than that of an early 80's B1. However, I didn't expect the difference to be so apparent, as the collector pipe into the silencer is far too close to the swing arm. There's no way the silencer can be fitted. Also the foot controls are in the way too.. though I want to raise them up anyway, so the kickstand clears the gearchange lever. 

And things were going so well... sigh..  



 

There is still a decent amount of clearance between the tank and the top clamp.

 


I put the wheels on an took some measurements today. I shortened the shocks as much as possible and set the forks to flush with the triples. I then lowered the front wheel until it was about 10mm lower than the rear (this allows for the difference in static sag later). Using the middle seting on the jig the rake was 24° and the swingarm angle was 10.5°. Technically the swingarm angle will be a bit larger as it is an unweighted measurement so both wheels should be at the same height. It is still OK at 10.5° though.

I am pretty happy with this as a starting point. I can lengthen the shocks up to 10mm if I need a larger swingarm angle. I can also lengthen the forks up to 20-30mm if I need more rake or just to keep the rake the same after raising the back end. Getting to 24° without needing to lenghten the forks was a best case scenario for me - leaves me with a good amount of room to tweek things once I've got it on the road.

 

Worked on cleaning up the brake panel, removed bearings and the swing arm, bushings were scored up. I’m going to put the new bushings in before blast and paint, I’ll seal the ends up.More NOS parts today.I’m thinking about rechroming the shifter, brake pedal and brake rod and the bracket.

With a new homemade spindle I could finally fit the rear end, though the bearing kit I bought for the swingarm didn't include any spacers, so need to find or buy whatever is required. Life would be easier if I could lift the bike off the ground, and onto a bike lift, but nearly put my back out trying on my own, so it can stay on its sump for now.

Made a start on the foot controls, chain drilled the mounts from 10mm alloy plate, test fit on the frame, showed I'd made another mistake. The brackets put the foot pegs 40mm lower than the standard position, so the gearchange side will need to be remade, while the brake side can be saved I think.

With the 43mm R6 forks off being rebuilt, I dug out an old pair of ZRX stanchions to try out the head light mounts. We weren't sure how big to make them, so they turned out to be way too long. So need to cut them back to bring the headlight back much closer to the headstock.

Dales rear swing arm is off a ZRX1100, I know I have the same basic setup.   However, there is a company call MotoGPWorks that sells a exact S1 swingarm replica for about $1300.00 bucks.  I found that the ZRX1100 setup is plenty strong enough, and raises the rear about an inch, thus slightly reducing the rake angle. I have about 3500 miles on my zrx1100 swingarm and I can definitively say it makes a huge difference in handling.  I also, at the same time, increased the swingarm pivot bolt to a 20mm using a ZRX rear axle, it fits perfectly.  I believe the last iteration of the twin shocker GPZ/J models frames are pretty dang good handling.  Their biggest issue was the spindly rear swing arm (frame wise) and slop in the bearing to pivot bolt connection.  Goes without saying the forks and rear shocks were lethal in stock form.  I swapped out the rears for a set of zrx1100 KYB's, which are light years ahead of the stockers, the forks were re-worked with  RaceTek springs and gold valve cartridge emulators.  I re-worked the emulators to get a tighter seal and a progressive type high speed valve spring.  I fine tuned the fork oil as well...this made a huge difference.  These old forks have way too large oil passage holes, they require thick heavy oil to actually dampen.  With emulators installed you can actually have high speed and low speed dampening.  

JM2C
577Nitro

I’ve made a lot of progress.  Let’s start with the brakes.

I didn’t plan to rebuild the entire brake system, but it sort of happened anyway.  

I had the rear wheel and swingarm off, so I had the idea that I would remove the rear caliper just drain to drain all the old fluid out, then put it back on and bleed it.  But when I pulled it off I found two things. First, one of the two bolts that holds the caliper halves together was about half-way out.  OOPS.



Second, it was clear the seals were leaking and the pads backing plates were rusty.  So it all came apart.



Based on recommendations here, I got a rebuild kit from Brakecrafers.  I bought the later style 79-80 pistons with the insulating disk.  I figured why not.  I had two issues with the kit.  It was missing the correct seal for the passage between the two halves, and the dust seals wouldn’t stay in place.  It seemed like they were too small, and would just pop off of the lip on the body no matter what I did.  I spoke with Brakecrafers and they were very eager to help sort it out.  Absolutely an “A+” for customer service.
I had already ordered OE parts to replace the kit parts before I spoke with them, but he assured me that the dust seals in the Brakecrafers kit were identical to the current OE parts.  This appears to be correct.  The OE part I later received looked identical.  I ended up cleaning and reusing the existing dust seal, which were fine and did not pop off.





And for good measure, I also rebuilt the rear master.



I used an aftermarket kit from Z1parts.net instead of the OE parts.  The piston wasn’t quite as nicely made as the OE part, but it looks like it will work fine.  

z1parts.net/kawasaki-rear-brake-master-c...r-repair-kit-kz1000/



 

Thanks for the link and tip on valve clearances. I own a couple of old Yamahas that require the occasion carb clean and they are really sensitive about cleanliness.  These carbs were in relatively good shape besides some varnish.  We checked/ measured all parts from the kits vs the installed parts.  These carbs don't appear to have been disassembled before.  We have a valve cover gasket on order.  I think it's better to have one on hand before disassembly.  Waiting on a lot of parts on order, there's quite a bit to do before it's rideable, front and rear brakes- I don't trust 44 year old brake shoe lining adhesive,  rebuild master and caliper, brake hoses, we need air box boots, rear brake switch, turn signal flasher, chain and sprockets, fork seals/ clean and rebuild,  steering head bearing clean and grease,  swing arm bearings clean and grease.  It's in amazing condition overall but there's safety items that I can't help but replace and or service before going around the block even.  I'll post some pics once I'm allowed to.   Thanks again!  

Well my 1975 build date A4 900 is done. I have put about 60 miles on it so far and it seems to be running in well.

Everything is original, or like original upgrade. I hade the factory gauges rebuilt and used the shorter turn signal stalks and mirror mounts. I have all new factory decals.
I installed the Z900 dual disc upgrade.

The changes to the suspension really made a the difference. I changed to caged bearings in the steering head and rear swing arm. The front forks got new tubes
and Racetech bypass emulators, the rear shocks are period looking rebound adjustable ICON shocks. the bike is very stable and predictable in corners.

The engine is completely brand new, only upgrades are better cam chain parts, 1st overbore, better valves and seats, rebuilt clutch basket and crank. I'm running it in on
brake-in oil.

Only problem I have had is with the fuel pipcock. When warn it only wants to run right on reserve. Im gonna go non-original and just run a Pingle valve.

Thanks for all the help everyone has given me. All total, I spent about 14k, including the cost of the bike. What do you think a 98 point A4 is worth?

Just back from seeing  the bike; I didn't buy it. It wasn't expensive for what it was, but I really wanted a more original bike - a lot of bits had been swapped out. Some of the original parts came with it, but weren't in a very good condition. Putting it back to good original condition would probably have soaked up more than the low purchase price would have given me. The motor was fine when warm, it just needed keeping in life with the choke when cold. The owner thought this was due to it having K&N intake filters.

It was indeed the starter clutch that had failed, but the handlebar starter button had also failed. 

I looked at the Zephyr swing arm, and then at the original. I must say, the Zephyr one looked really good, it seems it was a straightforward swap, just a spacer was needed for the swing arm pivot bearings. It had eccentric adjusters and generally looked a lot more substantial than the stock one. Maybe something for others to consider.

It was lovely to get back on a Z650 again after all those years, it rode and sounded as nicely as I remembered. Instant smile on the face stuff.

So I'm looking again...

Ian

I have a ‘90 Zephyr 550. It’s a great bike and the whole Zephyr series share many attributes, which I would say represent what happens when Kawasaki doesn’t “cheap out” on components. Dual disc floating rotors, aluminum box section swingarm with eccentric chain tensioners, tapered roller steering head bearings, and 4 into 1 exhaust all stock. 

From what I’ve gathered, they didn’t have much success because the timing just wasn’t right. They were air-cooled standards tuned for mid-range power at the time that some of the classic liquid-cooled super bikes were coming out.