KAWASAKI Z1325
With the engine in, Ralph wants to make sure this powerplant stays cool with an oil cooler.
Ralph Ferrand fits an oil-cooler to the powerful Zed.
Last month I slotted the big lump into the tricked up frame and started the onerous dry build of this super Zed. For me this is the most challenging and interesting part of the job, entailing much ‘on the fly’ design work and fabrication using many of the skills I was taught during my long apprenticeship at British Aerospace all those years ago. I delight in the challenge of solving problems with the caveat of making the solutions not just practical and safe but also aesthetically pleasing. Any bike producing a decent lump of power these days has the oil cooler on top of the engine cooling system, be it air or water cooling. The original Zeds were massively over-engineered and put out only a small amount of their potential horse power and so needed no extra cooling.
When you tune them as much as this bad boy, you most definitely need an oil cooler. Back in the day, Kawasaki did offer an oil cooler for its flagship four-cylinder four-stroke, but only for those tuned up for racing, and it was nowhere near big enough for this beast. My customer presented me with one he had found somewhere, but it looked more suitable for a lawn mower than this gargantuan motor, so it was duly rejected. I turned to the murky world of online sales sites to source a suitably capacious cooler for this bombastic mill and found a ten row cooler originally destined for a boy racer car: these are generally far more reasonably priced than similar items for tuned bikes. It obviously didn’t come with any elegant bracketry suitable for a custom classic motorcycle, but I could do that. I started with a piece of 50 x 50 x 3mm aluminium alloy extruded angle which I cut to length. I wiped it over with some marking blue and then marked the hole centres for the mounting bolts and the pipe connections on the cooler, which I then drilled on the pillar drill on top of some scrap wood. The large holes for the feed and return pipes were cut with a good quality bi-metal holesaw with plenty of cutting oil. When cutting with holesaws it’s best to cut the big hole halfway through first and then flip the workpiece over and cut the rest of the hole from the other side so the final bit to be removed is in the middle and you don’t get a horrid burr. I then finished the hole with a fine abrasive barrel sander in the Dremel, followed by a final rub with some dead emery, followed by a final polish with some Scotch-brite. I made some spacers from aluminium alloy round bar to bolt the top and bottom brackets into. I threaded them M6 at either end to take some M6 stainless cap screws. I finally gave them a quick polish to remove the extrusion marks. I then machined up some mounts to weld to the frame to attach the brackets to. These were short lengths of mild steel bar with a blind M6 threaded hole in one end. I initially marked out the shape for the top
bracket and drilled its mounting hole as M6. I then bolted the bracket to the mounts and lined them up on the frame and tack welded the mounts to the frame. I next removed the alloy bracket to prevent it getting too hot and fully welded the top brackets to the frame. I then assembled the embryonic brackets to the cooler and bolted the top one to its new frame mountings. This allowed me to calculate the position of the bottom two frame mounts. Once the lower cooler brackets were drilled 6mm, I bolted the lower frame mounts and tacked them in place with the TIG welder, removed the cooler and brackets and fully welded the frame mounts. One major Japanese innovation, when they took the motorcycle industry by storm, was their practice of using anti-vibration rubber mounting components which not only cut down on general vibration, but in doing so made the various sub-assemblies such as batteries, relays etc. far more reliable. Vibration causes stress fractures and bearing wear so the more parts of a bike that have anti vibration mounts the more long lasting and dependable the product will be. To this end, I used anti-vibration mounts for the oil cooler. The 6mm holes I had drilled in the aluminium brackets were then opened out for a set of Kawasaki rubber mounts that were used on the tail pieces of a Zed. The standard fayre was BZP (Bright Zinc Plate) steel ‘penny’ washers and bolts, but as always on custom work, I have upgraded them to A4 stainless steel. I have drawn a sectional drawing to illustrate how these dampers go together. The next challenge was to make a battery box, which on the face of it doesn’t sound too arduous, except that it was very difficult because the monoshock had used up valuable space where the battery box should have gone. I couldn’t afford to use a smaller battery given the engine is significantly larger and of higher compression, so the original battery size was very much a minimum spec. I actually fitted a modern AGM (Absorbent Glass Mat) battery to make available more cranking amps. AGM batteries are lead acid, but the electrolyte is absorbed by a very fine fibreglass mat and have significantly better properties than a traditional flooded lead acid version. The better quality ones are supplied dry and the dealer will fill and prepare the battery only when the customer buys it. Some makes are filled at the factory and shipped
‘live’ to the wholesalers and then in time to the dealers. The issue with this is that the battery has already started its life as soon as it is filled and so often when you buy the battery it has been ‘living’ for months or even years. By the time you install it on your bike it has lost some of its lifespan already. Quality brands such as Yuasa do not send out filled batteries and I would never buy a ‘pre-filled’ battery. My customer managed to source a donor battery box from some Zed that used the same battery. I was unable to use the same mountings so had to remove all the ‘fat’ from the donor. All the external bracketry was originally spot welded in place, so I had to drill the welds off. I centre punched each spot weld to be removed. There are special spot weld drills available, which are commonly used by body shops that have to remove lots of spot welded panels when repairing crashed cars, but I don’t have one. In the absence of a special tool, I drilled the weld so that the tip of the regular twist drill just passed through the first skin. I then replaced the twist drill with a slot drill as used on a milling machine which cut leaving a flat bottom, removing the spot weld but not making much of an impression on the main body of the battery box. There was a slight pip left, from the twist drill, but nothing that would affect the ultimate strength of the finished component. Once the box was cleared of all the bits sticking out that would prevent it fitting between the top frame rails, I had to add some brackets to attach it to the bike with its payload. Looking through my stock I spied a piece of used box section, previously part of a work bench, that was of the correct gauge, so cleaned it up and covered it in blue so that I could mark it up to be fashioned in to the perfect shape. Space was in very short supply so I needed to make it quite precisely. I made the brackets with the pillar drill, hack saw and hand files. Once made, each bracket had to be clamped in position using a small ‘G’ clamp and tack welded to the carcass of the box. When TIG welding them with the clamp removed, I had to ensure that I had good penetration, i.e. I had to melt the metal all the way through. It’s a tricky balance as there is no inert gas on the back of the weld so you have to be very precise not to burn the metal the other side and not to blow holes in it; it’s not the thickest gauge material out there, so this was challenging. A bit of a fettle and a bit of time in the bead blast cabinet and this part would be ready for powder-coating. Next month I’ll start by making frame mountings to attach the battery box to the bike, again using anti-vibration rubber dampers.