KAWASAKI Z650
He’s finally listening to ‘she who must be obeyed’ as Ralph gets to work on his wife’s Kawasaki Z650 clutch.
Ralph with part one of this clutch swop/conversion.
We bought SWMBO’S (She Who Must Be Obeyed) Kawasaki Z650 C3 many moons ago in a series of rather tatty cardboard boxes.
Some parts were duplicated and some came up short, but for £150 I didn’t think we could go wrong. How many times have you heard that line? The plan was to throw it together, get it running and think about throwing some money at it later on to pretty it up. Age and excessive consumption of locally brewed Butcombe bitter has not aided my ability to recall accurately, but if memory serves me right, we are now on the third engine. It always seems so much easier to just buy another ‘good’ engine than go to all the time and expense of a major engine rebuild. When the third engine wouldn’t play ball, I stripped it down to the last nut and bolt. I bead-blasted the whole engine and gearbox unit, sprayed it with etch primer, satin black, polished the shiny bits and bought it a Wiseco big bore kit. Because of its position, the starter clutch is a complete git to fix on a Z650, so I fitted a brand new complete unit and a new primary drive chain. The diminutive Zed has caused me no end of hassle over the years and has had more than its fair share of rides in recovery vehicles, though in recent years it has behaved sufficiently well that SWMBO has managed to clock up a good number of miles and smiles. Despite my hatred for the damned machine, the current Mrs Ferrand has insisted that Stinky (the side-stand mount is a bit knackered, making it lean over too far and thereby spilling petrol out of the float chambers if left for any period of time, hence ‘Stinky’) is her favourite bike and the only way it will be taken from her is from her cold, dead hands, mirroring my feelings for my 1977 Z100A1, which has been massively reliable. The mini-zed has always had an unnatural appetite for clutch cables, though SWMBO seems to cast a curse on
clutch cables on any bike she rides. As with all we aging folk, SWMBO’S hands are suffering from arthritis and in recent years she has been finding Stinky’s clutch painful to use. I was therefore commanded to make the clutch easier! There was no easy fix: weaker springs on the clutch basket would help, but the chances are the little bugger would repay this with a slipping clutch, particularly when she’s trying to keep up with my Z thou! The only solution I could see was to create some form of hydraulic system.
The earliest Kawasaki I could think of that had a fluid clutch was the GPZ900R and they made a shed load of them. The 900Rs are beginning to become collectable, but their used spares are thankfully still plentiful and affordable. She had a ‘random’ master cylinder on Stinky that I believe came from a Honda, so I decided to buy both brake and clutch master cylinders from a 900R so they would be matching. There was a certain amount of resistance to dog leg levers, but I pointed out that back in the day they were as much a ‘must have’ addition as a Harris exhaust. I managed to get a second final drive cover for the Z650, in case my modification went wrong, or she ever wanted to put it back to standard.
I started by buying a big lump of round aluminium stock, checking that it was of a weldable grade and machined up a rebated ring that the donor slave cylinder would neatly fit in. This was an easy job on the lathe. The next job was far more difficult and there was no guarantee it would work: I removed the machine vice from my milling machine and secured the final drive cover to the bed using a ‘T’-slot machine clamp set. I moved the table until the spindle was perfectly in line with the centre of the clutch actuator hole, which would be in line with the clutch pushrod that runs though the gearbox. The easiest way to achieve this was to put a centre in the morse taper of the spindle of the milling machine and drop it down into the 30+mm hole for the actuator body, moving ‘x’ and ‘y’ axis of the table until the taper of the centre lined up perfectly with the hole. I needed to bore a hole through the casing that would take the ring I made on the lathe. That means a BIG hole! For this I used a boring head fitted in the spindle.
This is a device that holds a boring bar, similar to the sort of boring bar you might use on a lathe, with adjustable offset. You set up the tool slightly larger than your pilot hole, in this case the 30-odd millimetres for the original actuator, then start the spindle turning and slowly feed the tool down through the hole using the ‘z’ axis control, which on most milling machines is the table moving up and down, but on mine the entire head moves instead. Once the cutter is back out
of the hole, the three machine screws that hold the carriage that holds the tool are loosened and a hex key is used to turn the micrometre adjuster the amount you want to increase the cut. The machine screws are re-tightened and another cut is taken. This is no picnic on a casting like this and one must be particularly careful not to take too heavy a cut, nor feed too quickly. As the hole gets larger then so the tool is cutting different parts of the casting, which is a mass of differing thicknesses and webs, etc. Only at the very start was it cutting all the way around.
As the hole got bigger so the jeopardy increased, with the cutter getting further and further offset. The larger the diameter of the hole, the more torque was being applied to the tool and the faster its peripheral speed got, meaning I had to keep slowing the spindle speed to maintain a suitable cutting speed. Once I had finally got the hole the correct size, I needed to partially counter bore it to allow the flange I had put on to the ring to be relieved into the cover. To set the size for the cut I fitted the ring into the hole and dropped the cutter down to the ring and adjusted the cutter to the larger diameter.
Having removed the ring, I had to very gingerly cut the counterbore. Because of the contour of the final drive cover it was only cutting on one side, so with such a hugely heavy cut I had to be enormously careful with the feed rate, so whilst it was a massive cut it was only taking a tiny sliver on each rotation. One false move on the ‘z’ axis feed and I could have done irreparable damage to my little milling machine and trashed the work piece. As it was, my use of extreme caution and patience rewarded me with a perfect fit. The GPZ900R had its slave cylinder painted black, but this bike has polished aluminium cases, so the paint had to be
removed. The paint gave way easily to an attack on the wire wheel on the bench spindle. Next it visited the differing grades of buffing wheels and polish at the other end of the spindle, and soon had a mirror finish to blend in with the cover. I had already bought refurb kits for the master cylinders and the clutch slave.
When I pulled the piston out, I was treated to the sort of corrosion and filth I had predicted, but the inside of its bore was a bit scabby, so I extricated the worst of it with extremely gentle use of some Scotchbrite, followed by a careful polish with a very small mop on the end of the polishing machine spindle.
If you’re going to do this, you must exercise great control and ensure that you keep all the movements very even or you will misshape the hole. With a good clean-up the piston was fine so I fitted a new seal and spring, lubed it up with some red rubber grease and replaced it in the cylinder ready for action. I then had to drill and tap the ring so the slave cylinder could be secured to it. I selected a centre drill with a 6mm mandrel and fitted in the chuck of my bench drill. I put a piece of gash 15mm MDF on the bed of drill to keep the workpiece flat perpendicular to the spindle of the machine. I jammed the cylinder in the ring with some paper to dissuade movement while I marked the hole centres. I very gently lowered the centre drill through the cylinder holes so that it would make a start for the tapping drill.
I then removed the cylinder and drilled three holes 5mm for the M6 thread. I used a 1st taper tap, lathered in RTV cutting compound to start the three threaded holes and finished them with a plug tap. Don’t waste your hard earned on cheapo taps and dies: budget taps are OK if you’re only cleaning crap out of threaded holes, but for this sort of work you really need the accuracy of good quality HSS cutting tools.