GPz900R Starter Clutch Replacement
Engine work begins
Boxing day 2007
Rather than stuff my face with Christmas leftovers I decided that some time working on the GPz motor would be well spent. The only fault that I am aware of in the engine is the starter clutch. So after reading the manual numerous times and picking the collective brains of the GPz owners club in the UK. It came to pass that the starter clutch can be removed by tipping the engine upside down and splitting the cases without having to strip the head and barrels.
Step 1
Once the engine is removed you need to remove the alternator and starter motor as there are bolts under them to hold the case halves together. Remove these M8 Bolts.
Flip the engine up side down and remove the oil cooler, sump and the oil feed that runs to the head. There is also an oil feed pipe running from the sump to the bottom engine case.
With the sump off, remove filter and the oil pump assembly. There are three silver bolts one is buried under the oil that remains where the filter sits.
Step 2
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 cover under it.
The covers must come off as they bolt to both the top and bottom cases in most cases. On the clutch side the chain that drives the alternator and is driven by the starter must come off, removing the bolt on the end of the crankshaft allows the gear to be removed and hence the chain can be freed but first the chain tensioner must be removed. Its spring loaded and will make itself difficult. The oil pipe mentioned earlier connects to the banjo bolt shown above the crankshaft.
The clutch should lift straight out, under it is the starter idle wheel which the starter motor drives.
With the clutch out the alternator shaft needs to be pulled back so it isn't engaged into the starter clutch, to do this the alternator clutch bracket must come off, it is held by a 12mm fasteners. The bracket is shown on the right. The alternator shaft is shown on the far left.
With the bracket off, the shaft comes out but does not need to be removed, it can just hang out the left.
The last remaining hurdle to remove the starter clutch is the gear that is driven by the starter motor. Its held in by an 8mm fastener that holds the shaft it spins on. Remove the shaft and the gear comes up, this allows the starter clutch to come out.
Success!
The starter clutch is now free, I drop the new one in and start assembling in reverse.
Of 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.
You can buy a kit to replace the roller and springs. Most people put a zzr1100 starter clutch in, it works exactly the same but is far superior.