Our Ralph this month is assessing the Big Zed’s general health.
Ralph Ferrand with part two: the heart of the Z.
Last month I started building the bottom-end of a fire breathing modified Big Zed. The original Z1 was no slouch, but this big block motor should chuck out some serious gee gees on the dyno when built. With an engine churning out so much more power than the original designer foresaw, it is essential that everything is in perfect fettle. The Big Z engines were massively over engineered back in the day and lend themselves to serious tuning. I’ll start this month with ensuring that the oil pump is tickety-boo. I tend to remove the strainer gauze first and ensure that it is 100% clean and is in no way restricting the oil flow. I cleaned it well with brake cleaner and lots of compressed air. I ensured that there were none of those hard lumps of crap that seem to get burned into the gauze over the years, probably from poor quality oil and/or negligence. I tend to carefully pick at the lumps with the sharp point of a scalpel. I always wear safety glasses doing this! When held up to the light one should be able to see through all the holes in the mesh. The next job was to ensure that neither the pump body nor the pump gears were worn. They rarely do wear, but one must be 100% sure with this. The pump was securely gripped in my bench vice with the obligatory soft jaws in place to protect this valuable component, and the circlip holding the gear driven from the crankshaft was removed and the gear was pulled off the shaft. The driving/locating pin was then removed and stashed safely followed by the washer behind it. Then the screws holding the cover in place were removed and the cover lifted off, revealing the gears. The gears were pulled from the body, taking diligent note of what went where. Everything was thoroughly cleaned with brake cleaner and I carefully removed the old gasket from both mating faces with a scalpel, taking good care to remove all the material, particularly around the location dowels. I very diligently visually inspected the pump gears and they looked fine.
I replaced them in the pump body and measured the clearance with the pump body with feeler gauges (see photo). According to Mr Kawasaki the standard clearance is between 0.011 and 0.083mm and so my measured 0.06mm is fine. There is a stated service limit of 0.14mm. Before replacing the cover one must ensure that the all-important location dowels are in place and that a new gasket is fitted. I applied a drop of thread lock and seal to the screws before I torqued them down to the setting specified in the manual; you really don’t want to be fitting Helicoils in your oil pump! I then replaced the washer and then the drive pin before popping the gear back on and securing it with a new circlip. Because this is going to be such a beast of an engine, it was decided not to just replace the starter clutch rollers and springs, but actually the whole clutch with genuine parts. The alternator rotor had hammer marks in it and didn’t seem especially magnetic so this was also replaced with a pattern item from Electrex World. I rebuilt the starter clutch onto the back of the new rotor. As you will see from the diagram, there is a rubber damper fitted behind the starter clutch gear. There are three different sizes of this part with a different depth of rubber lip. The clearance measurement behind the starter gear must be determined and then the correct damper rubber can be obtained. The smallest lipped damper for a clearance of between 5.06 and 6.05mm has a single star moulded into the rubber and has a part number of 92075-192. The next size up for a clearance of 6.06-7.05mm has two stars and the part number is 92075-193. If the clearance is between 7.06 and 8.05mm the part number is 92075-194 and it is identified with three stars. I have built many Z engines over the years, but this is the first where I have had to change this damper rubber. The one that came with the engine was incorrect.
Removing the old gasket – very carefully!
The bike as it was back in the day.
Remove ALL the gasket: particularly around the dowels.
Checking the clearance in the pump gears with a feeler gauge.
Use a torque wrench to tighten the cover screws.
Tightening the bolts that hold the starter clutch to the alternator rotor.
Fitting a new gasket to the pump itself.