Gpz900R Starter Clutch Removal and Repair


 

Before you start

The repair process requires dropping the motor from the frame, turning it upside down and removing the bottom half of the engine (bottom engine case). If you cant do that then guess what – you wont be able to replace/repair the starter clutch.

Difficulty scale – EASY but very time consuming, expect to spend 10hrs getting the job completed.

What you need

Setup

Drain the engine of oil and then remove the engine as per the service manual.

FinalAssembly 002

Carefully tip the engine upside down and secure it. You will need access to both sides and the entire bottom end. First remove the sump.

EngineWorkDec2007 003Then remove all covers that cross both case halves, we will split the bottom case off so nothing can be left on that attaches to the bottom case.

 

EngineWorkDec2007 005Keep careful track of the bolts and their locations, some reside in oil and some dont. Check the service manual to make sure which ones need liquid gasket sealant applied during rebuild.

  • 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.

 

EngineWorkDec2007 006Keep track of any cable clamps. They need to go back into the same spot.

 

EngineWorkDec2007 004With 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.

 

EngineWorkDec2007 001Keep track of all the parts! These are laid out as removed and cleaned before putting down. Try and keep everything spotless.

 

OR2008- 001Keep 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).

 

TopAndSideThis cover comes off and we can see the clutch basket (top right), crankshaft end (left with small HyVo chain) and the secondary shaft that the starter clutch sits on (bottom with chain behind it).

 

SAM_6761Take the ignition cover off and remove the disk, unbolt the sensors as they sit aside both cases.

 

EngineWorkDec2007 009Take the transmission cover off and remove anything that traverses the case halves.

 

 

 

Separation

 

EngineWorkDec2007 039

Carefully lift the bottom case off, most of the bits 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 dont 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 removed from their mounting point also during the disassembly.

EngineWorkDec2007 036Looking 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.

 

EngineWorkDec2007 016This 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.

 

EngineWorkDec2007 022

Under the input shaft is a bolt that holds a pin in. The pin is the support for a idler wheel that drives the input shaft when the starter motor is turning the starter clutch. Remove the bolt.

EngineWorkDec2007 023Then remove the pin and lift out the idler wheel.

 

EngineWorkDec2007 035Take out this bolt from the end of the secondary shaft on the right hand side. You should be able to pull the shaft to the left. There should be a cover over it.

 

EngineWorkDec2007 029The secondary shaft is driven from the end of the crankshaft. The toothed gear on the end of the crankshaft can be unbolted. Unbolt it now and then slide the secondary shaft to the left. Below the secondary shaft is the idler wheel we removed previously. Hold the starter clutch as you remove the shaft as the starter clutch is sitting on the shaft.

EngineWorkDec2007 027Success!!!! The starter clutch is now free to lift out and remove. Note that the secondary shaft is not fully removed and on the right is the cover over the right hand side.

The Starter Clutch

The reason the starter clutch fails to turn the motor is obvious when you understand how it works. The picture below shows the springs have failed and the rollers are not being pushed out.

EngineWorkDec2007 038EngineWorkDec2007 037Of all the failures in a GPz900R engine (there aren’t many) the prime failure component is the starter clutch. This one is a perfect example of what can happen. The roller is meant to be spring loaded but in these two photo’s I pushed the roller and it remained out. The other two rollers are OK, so the clutch kind of worked but could not fully engage. Toss the springs and fit your new ones.

Installation

Install the starter clutch and push the secondary shaft back in, bolt it down and pass the chain back over the crankshaft. If you cannot source GPz900R springs, you can use a set from the z650 and I suspect the z900 units (they never fail).

Push the idler wheel back in and secure it with the 8mm bolt you removed earlier. Now put the 8mm bolt back in on the other end of the secondary shaft.

Now reverse the remainder of the disassembly process but clean all the surfaces first and have new gaskets ready. Use the liquid gasket on the case halves so it is sealed and if done right wont leak.

When you re-align the counter balance shaft, set TDC on cylinder 1 & 4, find the small drilled mark on the balancer weight, aligned with the small oil hole on the crankshaft gear.

ZZR1100 starter clutch

I have heard that the zzr1100 starter clutch is a better option, however it is not a straight swap. Jan Ovv, a GPz900R enthusiast from Norway emailed me the process he used to replace the starter clutch.  The starter clutch gear is 3mm larger so the idler wheel has to be replaced as well. If you go down this path, try it and let me know what issues you encounter.

 

 

 

 

3 thoughts on “Gpz900R Starter Clutch Removal and Repair”

  1. David Meyer said:

    Curious if this is also a common issue, or an issue that could happen, on a 1987 GPz750r (Ninja 750r). I bought one a couple years ago that the guy said he had rebuilt the transmission on, but it wasn’t running well. I got it home, and after a few days, had issues with the starter engaging. I figure I’m on the right track to replace the starter (flywheel) gear as it was missing a few teeth, but I’m also wondering if this could be a factor as well. What are the symptoms that indicate the need for this repair?

    • Hi David,

      The symptoms are pretty easy to hear, you hit the starter and the starter motor winds right up while the engine may or may not (partially) turn over, usually the fault is the springs not pushing the rolls hard against the starter clutch shaft. If anything the teeth wont wear or get stressed as there is basically no engine load (the starter clutch is free spinning). Without seeing the total state of the engine, starter clutch teeth damage may well be just plain bad luck or age.

      • David Meyer said:

        Well then I’d have to say this is just a straight starter gear/flywheel issue, as the starter would sometimes engage but mostly would just make a grinding sound.

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