Kawasaki z900A4 Rebuild


Bike History

I purchased my 1976 z900-A4 in 1999 (significant other at the time wanted a new car and I wanted a zed.. guess which is worth more now 🙂  ).

The bike did not appear to have any previous registration history so this complicated the registration process (always get the previous rego label if you can).

Visually, the bike had numerous drilled holes where you would tie scrutineers tags and there appeared to be wheelie bar mounts behind the rear shocks, so I suspect the bike had been used for drag racing and may never have seen road time. It had lots of frame gussets and was rock solid so that was a bonus. I had to get an engineers certificate to get it registered and the proof of ADR compliance initially needed to be renewed every 5 years through the department of transport. This stopped a few years ago when I received a letter from the DOT telling me I no longer needed to re-apply every 5 years.

I had an accident in 2005 when the front pad seized while I was initiating a left turn down a steep hill, the bike literally flip over and landed on my hip, the rear of the bike hit the road while the front forks swung round and bent the steering stop pin, the frame suffered a twist and needed to be straightened.

Initially I fixed the damaged and then decided it really needed a full restoration. To keep the bike on the road, the restoration process has been done in small stages. The wheel rims have been re-chromed, hubs polished and stainless spokes fitted. Then other bits were rechromed and bolted back on.

From 2009 onwards the bike started to see a multitude of small problems grow so it was time to strip it and rebuild it! In the process it would get a new exhaust system and then lastly the paint job to replace the original cracked paint. As of 2020 the original paint is still on the bike.

Restoration Plan

To achieve anything in life you need to plan! To achieve the restoration or rebuild of a motorcycle takes a documented plan. Here was my initial wish list for the restoration of of my 1976 z900-A4.

  • Strip the bike back to the frame and get the frame straightened the extra bits cut off from it’s drag racing days DONE
  • Powder coat it satin black DONE
  • Powder coat the swing arm and fit new bushes DONE
  • Buy a set of 4 into 4’s! DONE
  • Find a set of left and right brake hose brackets that mount to the front guard (fender) and re-fit. DONE
  • Replace the green calipers with black ones and re-coat all black parts as needed. DONE
  • Recover Seat. DONE
  • Fix the dent in the tank and re-paint – TODO
  • Repair the side covers and repaint – TODO
  • Fill in the holes holding the racing number plate on the sides of the duck tail and re-paint – TODO
  • Change the handle bars to higher ones. Maybe Later
  • Strip motor for cleaning (water blasting) DONE
  • Rebuild the motor to stop the oil leaks and in the process water blast the cases clean first. DONE

Complete Restoration History

May 2007

After going on an 1100klm ride with my club ( our annual 1/2way ride (Brisbane to Nambucca Heads then out to Taylors Arms) followed by a 400klm day trip through the mountains a week later, a “high tide” mark appeared and the fork oil started to piss out of both fork tubes, it looks like the seals are shot and there is a long score mark on one of the fork tubes.

On the weekend of the 20th I disassembled the forks (about 30 minutes effort in total) and discovered that the score mark on the tube has also resulted in a score inside the lower fork leg.

The net result is that the tubes will need to be hard chromed to remove the scoring and I might need to bush the lower fork leg as the score is quite long inside the lower leg.

Later model bikes (GPz etc) have a top and bottom bush to alloy the tube to slide on inside the lower leg. Early model tubes slide “alloy to hardchrome” on a thin film of oil, which is OK if no grit gets in.

28th May – Update

The hard chromes were not to busy so the tubes are done and there are no issues. Also the lower fork leg is fine and does not need a bush. A light rub with some emery paper is all that is required to take the lip off the score inside the lower leg.

I also collected the lower triple clamp back from a small machine shop in a guys garage in the next street. The gentleman runs “Vintage and Classic Reproductions” which specialize in making dies and tooling for casting molds used to make vintage car parts. He was happy to use his EDM machine to burn out a broken tap that snapped while I was cleaning out the brake union mounting holes. He had to burn the hole to allow it to be tapped to 8mm but that is not an issue. I will be assembling the forks once I find what I did with the new seals. This week Wayne from Specialized Blasting Services called and my boxes of parts for the 3 other bikes are ready so its going to be a busy weekend!

June 2007

The front end rebuild went really well, the work done included getting the lower fork legs vapor blasted, clear coated and the fork tubes machined down and hard chromed. And the EDM repair to the lower triple clamp worked a treat. New oil was put in (170cc each leg) and the result is a really nice ride. I went on another club run and it rained for 2 hours and all through the night, the result was some difficulty in starting the bike which proved to be ignition coil wiring and possibly the kill switch. Once the bike was home I decided to strip it again and redo some parts of the coil wiring and am at present checking all the electrical connectors as a number of things like blinkers and parkers failed to work. Gotta love 31 year old bikes!

July 2007

The electrical system is still failing intermittently (I suspect an earthing problem) so I decided to strip all the wiring out of the bike and lay it out on the bench to figure out what is going wrong, in the process I will be trying to replace a broken connector and then try and recover the harness with new black cable conduit.

July Update

Well the bike is up and running after I replaced the coils and rebuilt the wiring harness. There was a faulty earth back to the battery so the bike was trying to earth through the headlight shell which was not working to well as an electrical conductor after the front end was rebuilt by me last month (new rubbers – no conductivity). I also removed the z1000 carbs and rebuilt the original ones and now the bike just needs the sync done with a set of vacuum   gauges. Its running well when off idle (idle is crap at present till the tune is done).

Now the bad news, the gear change has been loose for a while and the spline has now sheared so the bike was stuck in 3rd but at least I could cruise home! Should not be a major problem to remove it and put a different gear changer on.