KAWASAKI Z1325
Ralph again, on with part one of this Zed powerhouse.
When someone asks me if I can build a Z1000A2 motor the answer is: “No sweat, I can almost build ’em blindfold these days!” A Biker’s Toolbox customer rang me and asked me some technical questions about working on Kawasaki’s finest, the Z1000, and I was happy to proffer some advice. I had a look at a very interesting engine he has for a Rickman, which had a huge amount of high-quality period race tuning work done to it. A while later a now familiar South Wales voice rings up and asks if I could build up a Z1000 engine for him. I had already put a Z1000ST engine together for his brother in a short space of time, so I assumed this would be a similarly quick job: how wrong could I have been? It was explained that more than 20 years ago a rather over-confident young Welshman had rung the neck of his hard-worked, tuned Z1000 once too often and totally blown the engine to smithereens. He had stripped it and bought lots of very expensive, hot tuning parts for the bike and then, well, nothing really. He ended up buying another bike to abuse and the parts remained in a series of garages for two decades and sadly quite a few bits suffered from being in none-too dry lock-ups on occasion and some bits got mislaid. This was clearly no normal engine build and would test my engine skills to their limits. As the crankcases were pretty scuzzy I recommended getting them sent up to Steve Smethurst to get them cleaned to within an inch of their lives. They have to be completely stripped of everything including dowels and all studs. He then plugs up all the oilways etc. before vapour blasting the casings and then treating them with a mass vibration technique that leaves a finish better than new, which stays nice for far longer than with other techniques. The downside, from my perspective, is that when the casings come back, I have to clear out all the threaded holes by firstly blowing them out with
compressed air, then running a tap through them and finally blowing them out for a second time. This is quite a ball ache as there are lots and lots of threaded holes on a set of Z crankcases. Once cleared out, I mark the hole with a Sharpie to ensure I don’t miss any. Part of the vibro-process uses various sized ball bearings which can jam up a thread. You have to be very careful as a small ball can jam the tap making it easy to snap it off, leading to more work and costs. I had no problems with this build, but I did have an unseen ball unexpectedly jam a tap when cleaning out the carb rubber mount holes on a Z1A head once. I had to take the head to an engineering company with spark erosion equipment because this is the only way to remove a broken tap. The cost of that mistake has stayed in my mind for years, making me extra vigilant these days. I don’t think I have ever rebuilt an engine without having to drill out at least one broken off screw/bolt/stud, more often than not one or more under the final drive cover of a Z engine. So many DIY mechanics just ignore such things, seemingly in the belief that the manufacturer put in extra screws/bolts just for a laugh. They didn’t and trust me – no production motorcycle has any fasteners fitted to it that aren’t essential, even if the bike will lope along for a while with some missing bits. From my perspective, it tends to be better if the bodger hasn’t tried to put right their cock up, as removing sheared fasteners requires a fair degree of skill, so DIY attempts generally cause more damage. Drilling steel screws out of aluminium is quite difficult, because the drill always wants to wander off into the soft aluminium. Even when you have a small part you can clamp in the machine vice of an accurate milling machine, the drill will still try and take the path of least resistance. The answer is toolmaker’s buttons. These are hardened ‘top hat’ shaped bushes. As I didn’t have any proper toolmaker’s buttons of the correct size and given I wanted to get on with the job straight away, I made some temporary bushes on the lathe out of mild steel. They’re not ideal, but they got me out of a hole. I managed to drill a 3.2mm hole fairly concentrically in the remains of the screw using this method. Rather than try and drill the whole lot out, I thought it was worth a try with a professional extractor. I warmed up the area with the heat gun to expand the aluminium and squirted some ACF-50 at the offending article, which is a surprisingly good penetrating fluid, though it isn’t designed for that task specifically. NEVER use a cheap Easyout type tool, because you’ll likely end up snapping it off and paying money to an engineer with a spark erosion machine to remove the remains. I speak from bitter experience. Never put too much force on an extractor and if in doubt give it to an engineer to finish. I was lucky with this one and it came out without too much of a fight. In the photos you’ll see I had marked the hole ‘HC’ for Helicoil. If you can’t get the remains out like this, the chances are with a small M6 bolt that the threads aren’t going to survive, even if you are successful in drilling the inner part of the bolt out perfectly concentrically. Picking the remains of the bolt threads out of the threaded hole is pretty tricky and I would usually fit a Helicoil as a matter of course. The thread will have had too much torque applied to it for the bolt to have snapped off anyway. It turned out that the engine wasn’t a regular over-size engine, oh no, this has big block with
a swept capacity of 1327cc! The engine casings had to have the holes for the barrel sleeves machined out to take the massive big block sleeves. I was also given a set of APE 435 high-lift cams to use. Twenty odd years ago the head had big over-size valves fitted and some porting work to boot. With all the huge amount of extra power likely to be generated, a standard pressed together crank shaft would not be safe and could potentially twist, so we sent it off to be welded-up and dynamically balanced. If you look in the photographs, you will see a series of holes drilled in the crank-shaft webs, these are to remove weight in certain places to get the crank-shaft balanced. A bit like a wheel balance, but instead of adding weights you are removing weight at strategic points. The first stage of the build is to assemble the uber-heavy duty gearbox components and crank-shaft into the top crankcase. I can still remember my shock when I first opened up a big Z gearbox – they’re massive and so can deal with huge amounts of power. I use an engine build stand I made myself, which is great as I can turn the engine easily through 360°. Because this motor is likely to put out a whole heap more power than standard, I fitted high tensile studs to replace the standard bolts that secure the crankcases around the crank-shaft bearings. A new top-quality heavy-duty cam-chain was fitted, as it has a hard job dragging those massive, steep cam lobes around. I refitted the two location dowels front and back, the kick-starter gear and the odd triangular section rubber O-ring just behind the crank-shaft that is the main oil feed up to the top end. The steel ratchet gear arm stopper for the kick-start mechanism must have the tabs on the locking plate tapped against the hex flats of the two 8mm bolts securing it, to ensure they do not undo from vibration. The outer rings of the main bearings have shallow blind holes drilled in them which locate in small solid dowels in the top case. I have known people not line these up properly and I can assure you it makes a big mess that’s very hard to put right. These dowels are hardened and so if they’re forced in blind, there will be another trip to see the spark erosion man! One important reason for the dowels is that there is an oilway drilled into each outer race which must be lined up with the oilways that feed them in the crank case. I refitted the gearbox selector drum with the third gear selector fork, remembering to secure the guide bolts with a new tab washer. Don’t want that coming loose! Always use a new lock washer when installing the shift drum guide bolt. When assembling an engine unit everything should be lubricated with a mineral engine oil. There is a heavy bearing cap that is fitted over the inner-most roller bearings which is the last thing to be fitted before joining the cases and should be torqued down in the pattern specified in the workshop manual. This bearing cap has an arrow pointing forward and must be fitted the correct way around i.e. the way it was line-bored during manufacture. The mating faces on both cases should be scrupulously degreased using brake cleaner or a similar volatile, rapid drying degreaser. As always, I painted the mating faces with my old friend Wellseal, using a cheap nylon artists’ paint brush sourced from Lidl. I let the Wellseal flash off for 10 minutes and then carefully fitted the bottom case in place. The nuts were then carefully fitted to the 8mm studs that secure the crank bearings. The two outer rear ones need to have a light smear of silicone under the heads of the flange nuts. There are numbers cast into the bottom case near these studs decreeing the order these must be tightened in. I usually tighten them all down to 10lb-ft in the correct order and then to the recommended maximum of 19.5lb-ft. I then fitted all the 6mm bolts in place and used my ¼in drive torque wrench to tighten them all down to the specified torque of maximum of 95lb-in (8lb-ft). There is one more bolt head that
requires a smear of silicone under its head under the clutch at the edge of the sump opening. There are some more 6mm bolts on the top crankcase so once all had been tightened up on the bottom case, I turned the engine over and installed these bolts, omitting to attach the cable guides. Because this is a custom bike, there was no guarantee that the cables would run as standard so I decided I would address those later. I fitted the kick-starter return spring and its aluminium guide. I then refitted fourth and fifth gear selector forks with their shift rod. I’m not going into the gearbox build in much depth because it is, in my opinion, an easy job, providing you read the proper workshop manual, which can be bought second-hand off places like ebay or downloaded free, if you don’t mind infringing copyright laws. What is important is that you assemble each part EXACTLY as dictated in the manual. Some gearboxes e.g. BMW R100 gearboxes can be a tad tricky as you have to calculate shim sizes etc. While they are not complicated in real terms, they can be a bit challenging. Horizontal split boxes like Z1000s are a piece of cake. My first job next month is to disassemble the oil pump to ensure it is healthy enough to deliver a good dose of oil which will be needed to keep this fire breathing monster healthy.