This tutorial originally appeared on my z900collector wordpress site, however I’ve decided to move it to this site and publish it here with some very minor detail fixes and link the content back to wordpress.

There are also some references to this work in my book, you can read part of it here on google:

Before you start

The repair process requires removing the motor from the frame, turning it upside down and removing the bottom half of the engine (bottom engine case). You need to do this because the Starter Clutch is located in the middle of the engine.

Difficulty scale – EASY but very time consuming, expect to spend 10+ hours getting the job completed if you have never done it before.

What you need

  • Gasket set for Engine Side Covers – Available from the GPzZone UK Shop.
  • Liquid Gasket (3M Threebond – also sold by each manufacturer i.e. “Kawasaki Bond”
  • Starter clutch kit (springs at the minimum).
  • Tools
  • Suitable Car Jack
  • Clean work area
  • Oil filter
  • Fresh Oil

Getting Started

The first two things you need to do are:

  1. Drain the engine of oil and
  2. Remove the engine as per the service manual.
The engine is ready to remove, place a jack under it to take the weight.

Once the engine is removed you need to carefully tip the engine upside down and secure it so it does not rock around. You will need access to both sides and the entire bottom end. First piece to remove is the sump, then the clutch cover.

Here the engine is upside down and we can see the sump and clutch cover has been removed.

You will need to remove all the Engine Covers that cross both case halves. We need to do this because we will split the bottom case off, so nothing can be left on that attaches to the bottom case.

Handy Hint – Keep track of any cable clamps. They need to go back into the same spot.
Another Handy Hint – Keep careful track of the bolts and their locations, some reside in oil and some don’t. Check the service manual to make sure which ones need liquid gasket sealant applied during re-assembly.
  • Remove all the 8mm bolts that hold the cases together, there are 3 in the sump and 6 that hold the crankshaft directly.
  • Remove the 6mm bolts that hold the cases at the front and the 3 long ones at back of the engine.
  • Remove the side cases – clutch cover, ignition cover and chain drive cover.
  • Remove the sprocket and remove the transmission cover under it. Be careful of any seals, avoid damaging them or oil may leak out later.
With the sump off, remove the filter and the oil pump assembly. There are three silver bolts one is buried under the oil that remains where the filter sits. Remove the oil pipes and gauze.

With the sump off, you need to remove the oil filter gauze and plumbing. Then you also need to remove the oil pump, one of its set screws is hidden in that puddle of oil you can see above.

Keep track of all the parts! These are laid out as removed and cleaned before putting down. Try and keep everything spotless.
Keep track of this little piece as well, the first time I took a GPz900R engine apart this poped out and it took ages to work out where it went (rear of the engine).

While the timing disk is part of the crank, the sensors sit over the two cases and need to be unbolted at this time. There is no special alignment for them during re-assembly.

Take the ignition cover off and remove the disk, unbolt the sensors as they sit aside both cases.

The next component to undo is the Alternator Shaft, you need to pull it forward after you release the chain. In the photo below, you need to undo bolt “A”, then release the tensioner and finally unbolt bolt “B”.


Once all the cases that attach to both halves of the engine are removed, as well as the oil pump, you can then work towards removing the bottom engine case, two things to note, the shift dogs for the gears and the Counter Balance shaft are located in the bottom case, read the service manual on how to align the balance shaft before you pull the case off so you can re-align it during re-assembly.

Carefully lift the bottom case off, most of the components are in the “top” case, which is facing down at the moment. The counter balancer is in the bottom case and drives off the crank, its alignment will change when you lift off the case. It will need to be reset when we re-assemble the cases. If you don’t reset it back to the correct orientation to the crank you will end up with lots of additional vibration.
Notice the ignition timing sensors are just hanging free.

Looking at the top case we can now see the Starter Cluch Assembly, to access it we need to lift out the clutch basket and gear set. It’s heavy so take care.

Looking at the top case, we can now see the starter clutch just above the clutch input shaft, to get to it we need to lift out the clutch basket.

Once you lift out the Clutch Basket, you have full access to the Starter Clutch and Idle Gear

This shot is slightly out of sequence, I removed the secondary sprocket and pulled it to the left, then I picked up the clutch assembly. First you need to remove the clutch assembly then unbolt the secondary shaft as show below.

Here we have a clean shot of the Starter Clutch, the Alternator Shaft has been pulled back out so we can now lift out the Starter Clutch.

Before you lift out the Starter Clutch, unscrew this set screw which holds the idler gear, then remove the pin it sits on.

I’ve tipped the Starter Clutch on its side so you can see exactly where it sits.

With the Starter Clutch on the bench, we can see the problem, the roller is not being pushed against where the free spinnning gear sits. This is due to a worn or broken spring. The three springs should be replaced at the same time.

Check the housing for cracks and check the pins and rollers for obvious wear, or replace the lot for complete satisfaction 🙂

Replacement springs are easy to obtain, you can see in the picture the remains of the damaged spring. This picture is from a z650 starter clutch which can use the same springs as the GPz900R.

Once you have replaced the three springs and checked the assembly you can now begin the re-assembly process.

Basically you need to reverse the process. The following list will match the photos in reverse order.

  • Clean all gasket surfaces meticulously.
  • Fit Starter Clutch to Alternator shaft and push in place.
  • Fit Idler Gear back in place, install shaft and tighten down the set screw.
  • Re-install the clutch basket.
  • Put the Alternator chain and Tensioner back in and screw down the set screw on the Balancer Shaft
  • Clean all mating surface and apply liquid 3M Three bond to the case halves.
  • Fit bottom case, noting gear change dogs and Balance Shaft positions.
  • Re-fit the oil pump and plumbing.
  • Re-fit ignition pickups.
  • Clean all side cover gasket surfaces so they are spotless.
  • Fit new gaskets.
  • Fit side covers.
  • Fit sump and oil filter.
  • Tip engine back up and jack back into frame, fit bolts and torque to correct setting.
  • Re-fit rest of engine/frame parts.
  • Re-fit cooling plumbing.
  • Refill oil
  • Start engine!

Final note, check the balance shaft timing as per the service manual, it’s really the only re-assembly issue you will have if you methodically follow the re-assembly steps in order.