More heavy metal!
Project Big Zed part 6
Last month I started to fit a PMC frame stiffening kit to the mighty Z1325 custom bike. This month there will be more fabricating and machining, to the frame of the original Z1000A2, but I’ll start with making a new set of engine mounting plates. The originals were not very thick mild steel plate and I thought that for this puppy I would upgrade to lightweight but stiffer 10mm aluminium alloy plate.
I started off by wiping engineer’s marking blue on the face of the piece of 10mm aluminium bar selected for the job. I initially marked the hole centres with a scriber. I then centre punched these and used the punch marks to scribe the radii of the triangle’s corners. I then joined up the radii marks with a scriber and steel rule. When scribing a job, always ensure that no lines go on any remaining surface i.e. outside the cut marks, particularly if it is to be polished as this job was. I then centre drilled all the holes in all the plates in the pillar drill and then pilot drilled them. Those holes that had to have threads cut were then opened out to the tapping drill size. I then clamped the bar in the bench vice and tapped out the holes. I used a first taper tap to start off with to ensure that the thread was perpendicular to the plate, before running through with a second taper and finally a plug tap. I then opened out the remaining holes to their final sizes. When drilling and tapping I always use Rocal RTD cutting compound or fluid because it not only doubles the life of cutting tools but also cuts down on heat and gives a better finish. I then took the piece of bar to my band saw. It’s not a mega machine, sadly, and Elektra Beckum do not sell it as a metal cutting saw, but with a fine-tooth narrow bi-metal blade it fairly zips through aluminium alloys and leaves a nice square edge. I then filed them to the size and finished the edges off with draw filing and then with dead emery cloth wrapped around the file: this is emery cloth that has been used and has lost much of its abrasive sharpness and gives a very fine finish.
The original ‘builder’ of the frame (loose term) had made a particularly ugly job of the top shock mount, between the rear cradle tubes and because this was likely to be visible behind the pod filters, I decided to hide this abortion with an aluminium alloy cover. I found a suitable piece of alloy sheet and covered it in engineer’s marking blue. I then marked it out with an engineer’s steel rule and a scriber, being careful not to put any marks on the face that would be seen. I cut out the outer shape on the bandsaw and filed it to size with a dreadnought file, then draw filed it to final size before getting a nice edge finish by draw filing with a piece of dead emery cloth. I marked the bends with a Sharpie, because firstly scribed lines would ruin the finish and secondly because they can cause a stress fracture when being shaped in the folding machine. I decided a brushed aluminium finish would be suitable and used a Scotch-brite wheel on the polishing machine spindle to achieve it. I later sent it off to be anodised to protect the finish. I next gathered together lots of aluminium parts to take to Mikey’s Polishing Shop to get him to work his magic. While I do my own polishing, if I have a lot or some particularly difficult stuff for other people’s bikes I tend to let Mikey do it. He’s been polishing since Stonehenge had a roof on it and will always make a better job than me. It is a fairly filthy, unhealthy job that requires great skill to do well and I like it less the more I do. Having a good linisher is of paramount importance and a good collection of belts, not graded just by their grit size but also by their level of knackeredness. A new sharp belt is good for certain jobs, but a heavily worn belt has its uses as well; the same as dead emery cloth. The surface of a scabby bit of metal can be looked on as a field with peaks and troughs. Basically you have to remove metal evenly to the level of the deepest troughs. You use a coarse abrasive to hack though the majority of the excess metal. As it is coarse it will make its own troughs, but providing they are no deeper than the target depth it doesn’t matter, because as you use finer and more worn linishing belts new troughs get progressively shallower. Once linished, Mikey then changes to buffing wheels, which have a polish
applied to them which is actually a grit – albeit a fine one. He starts with the most course grit polish on a sisal mop, through medium grade polishes and stitched mops and finishes with the finest polish on an open linen mop. At the end he uses a Vienna lime powder and finally has to remove all the grease etc. from the polishing compounds with a solvent and a soft cloth. I have clearly simplified the process, somewhat! Having had Mikey work his magic on the one off top yoke, machined many moons ago on a manual milling machine, to take the Suzuki GSX-R750 WP front forks, it transpired that no one had thought to make provision for a set of clocks and this customer had been going to fit some nasty modern binnacle, robbing the bike of an essential part of its true Zed DNA. There are certain parts you can’t take off a Zed, if it’s going to look like a Zed and the clocks are an important part of that period look. The yoke had a facility for fitting an ignition switch into it, but as the mount for Zed clocks have a position for the key switch, I decided that the best thing I could do was to remove this part in the milling machine. I carefully clocked it in to the machine vice with a DTI (dial test indicator) and then used an end mill to cut away the lump that was going to be in the way of the new (original) clock mount. I then did some Mikey-type polishing to hide the join. On the stock Kawasaki yoke there are two holes with specially cut tapers to take the damper rubbers that provide the anti-vibration mounting for the speedo and rev counter bracket; vibration being the enemy of the delicate instrument. I had my work cut out to make an attachment to fit the custom top yoke to attach the instrument bracket and retain the anti-vibration qualities; I don’t mind
telling you that it took some serious head scratching to work out how I was going to cut two accurate opposed tapers in a big lump of aluminium, but as they say, desire is the mother of all perversion (or something like that) and I finally came up with the idea of using the lathe and its four jaw chuck. Firstly, I machined the block square and to size with the milling machine and then covered the block in marking blue. I marked up the centres for the two holes with a vernier height gauge on a surface plate. I then set up the block in the four jaw chuck so that the centre in the tailstock was exactly lined up with the first of the hole centres. I then centre drilled it using the tailstock chuck and drilled the hole out, using a succession of drills until the hole was slightly less than the smallest diameter of the taper (Ø X on the drawing). I then set up a boring bar in the tool holder. I used a vernier protractor to measure the angle of the taper and set the top slide on my lathe to that angle. I locked the saddle on the lathe and used the top slide to run the boring bar through the hole, altering the cut each time with the cross slide. I kept removing material until the largest diameter of the hole (Ø Y on the drawing) was the same as a genuine Kawasaki top yoke. I removed the workpiece from the chuck, fitted the last drill bit for the initial hole in the tailstock and slid the hole of the work piece onto the drill and pushed the tailstock down the bed and used this as a datum to set up the four jaw chuck to grip the block ready for me to turn the second taper. Once it was close, I removed the tailstock and clocked it in accurately with the DTI (Dial Test Indicator). I was then able to repeat the taper turning method previously employed on the other side. Once finished I repeated the whole exercise for the second double taper hole. Once the holes were machined to my satisfaction I milled the block so that it would neatly attach to the existing yoke and cover the hole made for an ignition switch. The last job was for me to fire up the polishing spindle and ‘Mikey’ it to a good shiny finish and bolt it to the yoke. When I was handling the yoke on the bench a bit fell off it. It was this that made me realise that all those years ago it had been manually milled and someone had dropped a teste. You can see from the photo that a piece had been neatly welded in to cover the cock-up, but sadly did not have enough weld penetration. At this point I had to get the piece re-welded in by a top coded welder. I’m okay at general fabrication TIG welding with aluminium, but this required the hands of a serious specialist to be right and more to the point safe: this bike needed to be 100% safe!