KAWASAKI Z1325
Ralph is back with this very special ‘special’ Zed. He’s getting close to the finish line
Ralph sorts the clocks out
I’m back again with the major build of an extreme special based on Kawasaki’s flagship motorcycle of the 1970s. The bottom end of this fine bike was massively over-engineered and as a result, long after KHI had moved on to the ultra-modern water-cooled engines, there were lads around the world tuning the living poop out of Zed motors, producing well in excess of 500 horsepower to propel their drag bikes at vision-blurring speeds. For this level of insanity, the earlier cases were required (Z1, Z1A or Z1B) as they had some extra webbing and the inner crankshaft bearing cap would need a steel plate added. To get this level of power, forced induction and a dose of Nitrous Oxide is required. Just about everything has been inflicted on a big Zed motor over the years, and they keep pushing out the horsepower and coming back for more. This bike has a pretty hot engine to say the least, and should embarrass many a modern superbike in a straight line. For me, however, a custom bike based on a classic should retain as much of the character of the original bike as possible. There are certain elements of a Big Zed that must be kept if you want to finish up with a Zed rather than a bike with a few Zed bits on it. The first thing you always notice about a Zed is the beautiful shape of the tank, side panels and tailpiece. The clocks and headlight set up is another important feature which defines the breed. I have seen too many classic bikes with their looks spoilt by nasty, pervasive mini indicators, which do nothing for safety or looks. This bike had lost its iconic locks, but thankfully there are now specialist companies making new pattern speedos and rev counters. Because the tacho drive part of the cylinder head had been damaged back in the mists of time, without some serious machining work it wasn’t going to be possible to reinstate the mechanical drive from the exhaust cam, but luckily the makers of the new clocks possibly envisaged this problem and supply an electronic rev counter, which looks just like the original. A pulse from the ignition coil feed tells the tacho how fast the engine is turning. Also available are all the instrument mountings, idiot lights, rubbers, fasteners and bulb holders. Whilst we might have been able to source some used clocks and refurbish them, it was far more cost effective to fit new, and trying to fit electronic guts into an old clock would be challenging in the extreme. These items are available through Z-power. Next up this month I fitted the wheel spindle adjusters to the Suzuki swingarm. I had got all the components refinished with bright zinc plating, making them indistinguishable from new. I locked two nuts together to install the studs into the arm, and treated them to a dose of stud lock and seal to prevent them undoing as a result of vibration. I gave the adjusting nut a drop of ACF-50 Corrosion Block grease to help lubricate it and also protect the
threads from corrosion. The body of the wheel adjuster then slid over the special nut and was secured to it with a circlip. When I came to refit the starter motor, the forward bolt would not clear the fins of the big block, so clearance had to be made. Originally the bolts would have been M6 flange bolts, but there was no way I wanted to hack enough out of the barrel fins to take one of those. I popped an M6 button head screw into the hole, as its lower profile made it better to scribe around to mark the fins with a cranked scriber than a cap screw. Once marked, I grabbed a 90-degree-angled windy drill from my aircraft days and fitted it with a burr (rotary file), using it to cut away just enough of the offending fin to get an M6 cap screw through. I then sucked up all the swarf with an air-powered mini vacuum cleaner, a very useful device for sucking up in restricted areas. Stock bikes had BZP mild steel exhaust studs, initially M6 on the earlier Zeds, but after numerous failures, these were upgraded to M8. They are in a particularly vulnerable position, getting all the filth chucked up from the road by the front tyre as well as being heated by the exiting exhaust gases, so to keep a nice finish with longevity, this engine had upgraded stainless steel studs fitted with a drop of stud lock and seal to prevent them undoing with the nuts. I fitted them with a stud installation tool, initially whizzing them in with my 3/8” drive impact wrench to save time, and then finished them with a torque wrench. Whilst you can use two nuts, it takes a lot of time compared with an installation kit, which is not expensive.
I have built a lot of Zed motors over the years and one thing I have learned is that if the engine has the original alternator windings, they will want replacing. Electrex World sell a top-quality pattern winding for £66 including VAT, so it’s madness not to fit one. Even if the system was charging before the rebuild, the chances are that it will get disturbed and will fail either immediately or soon after installation. The original regulator with separate rectifier are usually on their last legs and can cause the premature demise of the battery and sometimes the alternator windings, so I tend to change them out at the same time for an Electrex World reg/rec, which is only £72 at the time of writing. Zeds are famous for incontinence, stemming from the Ac-wiring coming out of the alternator. Experience has taught me that there are no short cuts to sort this. I slid the new winding into place in the casing, which is a perfect fit with no slop. Three M5 screws with a drop of thread lock hold it in place. The alternator wires, the special grommet (which comes new with the winding) and the alternator need to be OCD clean and free from any form of grease. This is best achieved with lots of brake cleaner and/or panel wipe, together with plenty of elbow grease. The pocket where the wires exit the casing should be literally filled with good-quality RTV silicone. The round recess where the wires enter the special grommet should be packed with RTV and the cutaway grooves in the grommet. The wires should be pulled in and out of the grommet to ensure the RTV gets in the holes. The grommet was then fitted into its place. I have a
special tool I made many years ago to cast the silicone seal perfectly. I made it from some sign maker’s Dibond, a composite sheet of aluminium sandwiching polythene which is nicely rigid. I apply furniture polish to it to act as mould release, i.e., to stop the silicone adhering to it. I then use the two holes either side of the wire exit to bolt it up. There is a cut out to prevent the wires getting trapped. I usually leave it to set fully overnight. As usual, this made a perfect seal, which didn’t leak. This is my own development and you will not find it in any service manual, but it works. I found a few more stripped threads when I came to bolt up the casing to the engine. Another result of someone not using a torque wrench! I use the bestquality industrial genuine Helicoils, not for a fashion statement or because I am
stinking rich, but because the cheap ones simply aren’t as good and can cause problems in the future. Remember: ‘Buy Cheap, Buy Twice.’
Thanks to: www.bikerstoolbox.co.uk www.z-power.co.uk www.electrexworld.co.uk