1973 Kawasaki Z1 900

On Halloween, 1973, I appeared at a Kawasaki shop to pick up my new bike. I had never ridden a big Kaw even as a passenger, but I was sufficiently impressed with the reviews and what I saw to make a fairly easy decision. I was somewhat tempted to go for the 750 two stroke. The Z1 cost me an even $2,000, versus about $1600 for the 750, but I had concerns about the durability of those bikes, and they didn't offer any performance advantage. The large size of the Z1 wasn't particularly to my liking, but it seemed to carry the weight well and I had no fantasy I would keep the bike stock.

I had never ridden a four banger before, the closest relative the Z1 I had ever experienced being the H1 500 two-stroke or the Honda 450, if either of these can be considered close (actually the Honda was very close, mechanically, but more on that later). After taking care of the paperwork, I went out and hopped on the machine, excited about my ride. The shop had an unusual parking lot, steeply sloped down to the entrance of the service area. As I motored away, up this steep incline, within the first 30 feet I almost stalled the motor. I pulled in the clutch and started rolling backwards, to the excitement of the shop owner and mechanic witnessing my departure! No problem - by the time I had gotten all the way back to my original starting point, I found the brake and reminded myself that, impressive horsepower figures notwithstanding, this motor did not have the low-end grunt of my Sportster. After an embarrassed attempt at explaining my unfamiliarity, I applied a more liberal amount of throttle. I managed to maintain my forward progress this time, riding home without incident.

My initial impressions were, of course, favorable. After you spend 2,000 1973 dollars, you don't have much choice but to feel good about your purchase if at all possible. I kept the revs below about 4,000 in deference to the new motor, but this was still good for just over 60 MPH. The first negative impression was the drive line snatch, which I considered quite pronounced at the time. A few days later, however, I had gotten completely used to it and didn't think it was at all bothersome or even noticeable. The braking performance left a more lasting impression. The Sportster's brakes were miserable, as were most of the brakes of earlier vintage machines. Honda had introduced disk brakes on mass production machines in 1969. Within a couple of years all big Japanese bikes had disks on the front, and their superiority was such that Harley racers unashamedly adopted Japanese brakes as a solution to stopping their American iron. The Kawasaki had the by now standard single disk on the front matched to a drum rear. After years of wondering if I was going to really be able to stop in time, the new brakes seemed like free insurance. But, having only one caliper, the pull to one side while braking heavily was something that took a little getting used to. This was commented on in the first road tests of disk-braked bikes, but with everybody now adapted, this phenomenon hasn't been mentioned in 20 years.

These first-year Z1's met every challenge with brute force. Think the power and weight might cause excessive chain wear (chain problems on the first CB750's were legendary)? Hang on the biggest chain known to motorcycling, a #630, and, for good measure, add a sprocket-driven oiler. Kind of big and messy, yet confidence-inspiring. Just get used to lots of black oil spots on the backs of your shirts and jackets. Everything about the Z1 was big and clunky, like an old Chevy, compared to other Japanese machines. The sound of the fully muffled stock bikes was, at cruising speeds, dominated by the whine from the sprockets and straight-cut primary gears. That Kawasaki used such a simple and efficient arrangement, despite the fact that straight cut gears are nosier than primary chains or helical gears, was typical of the straightforward, in-your-face engineering that made the machine such a success. There really wasn't anything particularly innovative about the Z1. The engine design looked to have been largely lifted from the Honda 450, so much so that some of the parts, such as the cam chain, could be interchanged. Kaw pistons could be used for Honda 450 big-bore kits. Kawasaki, however, got conservative (thankfully) in the avoiding use of the Honda 450's steel head inserts and torsion bar valve springs.

I broke in the new engine carefully, during the second stage allowing 6,000 RPM. This engine speed translated into more than 90 MPH, a speed at which the Z1 felt like it was just beginning to really gallop. My Sportster would, of course, also run 90 MPH all day long, but it's just that, with all the noise, vibration, and right leg stuck out into the wind to avoid the carburetors, you couldn't ride it for very long at those speeds.

In accordance with Kawasaki's requirements under the terms of the warranty, I returned the machine to the dealer for service at the specified intervals during the meager six month/6,000 mile warranty. I was duly charged for a full tune-up and valve adjustment, but after these visits I could never discern any evidence that the machine had been worked on. My suspicions were re-enforced when the machine came off warranty and I endeavored to do my own valve adjustment. Upon finding some valves a little out of adjustment and calling the shop in search of the appropriate size replacement shims, I was informed that they didn't even stock them. When I asked how they ever managed to adjust valves, they incredibly responded that, even though these bikes had been roaming the streets for well over a year by then, they had never come across one that needed valve adjustment!

I was entirely satisfied to keep my new bike stock for at least a little while, only modifying it by fitting the ubiquitous Gran Turismo handlebar grips and removing the right side mirror, passenger grab rail and kick starter lever. A few months later, however, some careless and anonymous driver tipped the pristine machine onto its side, leaving a dent in the tank right at the badge. Restoring the stock paint job would have been expensive, so, without too much regret, I decided to distinguish my machine from the growing number of other Z1's by spraying on one of my own creations. While I was at it, I eliminated the rear fender by fashioning mounts for the tail light and license plate on the molded plastic tailpiece. This was a decade or so before the term "fender eliminator kit" began to appear in magazine ads. Another three pounds saved!

The casual way in which the Z1 moved the earth beneath you was always a thing of wonder, but even more so in that age of anemic, antiquated twin cylinder machines. The motor wasn't really rev-happy, and you could ride it around all day without going over 4 or 5 thousand RPM and still get the feel of a strong, capable machine. But when you cranked it up beyond 7,000, things really started to happen. The nationwide imposition of the 55 MPH speed limit not too long after I got this machine was unfortunate since the Z1 would accelerate to that speed without shifting out of first gear! To convince an incredulous buddy (Wayne Meglan) who was used to the chug-chug of his Panhead, late one night I stuck him on the back of the Kaw outside a bar and headed for a freeway onramp just down the street. With my eyes focused on the tach and speedometer as we accelerated onto the highway. I somehow didn't notice until it was almost too late that this entrance ramp wasn't really straight! At least that incident taught me a lot about the bike's cornering ability with a passenger, but I prefer to learn these lessons in a more controlled fashion. Another incident which confirmed the machine's excess of talent was the winter day when I was riding on Highway 70 in downtown St. Louis with Jocelyn Wilkins as my passenger. I looked down at the speedometer to find that I was doing 90 MPH. I guess I must have been distracted.

Aside from paint and removing a few extraneous bits, the first change I attempted to make was handlebars. I picked up a pair of clubman bars somewhere, and one evening endeavored to fit them to the Z1. Clubman bars are so called because they were legal in club races, which required that the handlebars be mounted in the stock position, which is to say, in 99% of the cases, to the top of the triple clamps. They were bent and welded such that, mounted as intended, they gave about the same riding position as clip-on handlebars. I wanted mine mounted the other way around, however, so that I would have nice, narrow bars with just a slight rise. This first pair, however, didn't fit, the bulk of the switches and master cylinder being too much for the short bars. I later glommed onto a pair of Denco bars, which worked quite well both upside down and rightside up. I liked them so much I still own 'em.

After the handlebars, the next thing to change was the exhaust system. I wasn't a real hot dog who wanted to make lots of noise and get that little extra power that aftermarket exhaust systems promised, but by the time the bike was only about 1 1/2 years old, the stock mufflers had started showing wear and tear. The packing came out of one, sticking ridiculously out the end of one pipe, and little rust spots were all over the place. These original exhausts were one-piece from the header pipe on back, with everything welded together, so re-packing and re-chroming didn't seem like a feasible option. I couldn't even figure out how to get at the baffles. So, after much shopping around, I opted for an unchromed Yoshimura 4-into-1 pipe that a local shop said they would let me have for a cool $100 (5% of the machines purchase price). This pipe was optimized for roadracing, I knew, giving maximum ground clearance but it ran right down the center of the bike so that the center stand had to be removed, and you couldn't change the oil filter without taking off the one-piece collector. I could live with that. I would have actually preferred a Kerker, but wasn't ready to part with an extra $50. I had my wife pick up the new pipe for me, but when she got it home I found out that it didn't even have a muffler! I called the shop to complain, thinking that they must have surely forgotten to give me some parts. Their explanation was that it would be just fine if I got one of those tail cones from the end of a Suzuki GT750 muffler and stuck it in the end! I knew that this would provide next to no silencing at all, but it did at least give me a starting point in rigging an effective muffler. I rummaged through my junk and came up with a perforated tube from a real muffler. Around that core I wrapped as much fiberglass furnace filter material as I could jam into the 3" wide pipe and, somewhat surprisingly, I had a pretty decent muffler. Since my Harley experience had legitimized sheet metal screws in motorcycle applications, I used those to secure the Suzuki muffler tip.

The greatest pleasure in riding the Z1 was to be found out on the highway, where the relatively large size of the machine became an attribute. The longest trip I made was a ride from St. Louis to Bloomington, Indiana in the summer of 1975. Before the imposition of the 55 MPH speed limit, you could cruise along all the way across southern Illinois at 75 or 80 without feeling like Dillinger. I really let it hang out on the way back, however, running 85 or 90, and occasionally 95 MPH all the way from Terre Haute to just outside East St. Louis. At 95 MPH, in the normal riding position, handling was uncomfortably vague, but any speed below that felt perfectly natural. Fuel consumption, however, was nothing to write home about. I would only get a little over 100 miles out of the 4 2/3 gallons of gas my tank held. Once I forgot and left the petcock on reserve, with the result that I sputtered to a stop midway in the trip. Fortunately, the Z1 tank had a central tunnel that kept a little extra fuel on the side opposite the petcock, and I was able to lean the bike over and slosh enough gas into the carbs to make it to the next filling station, though not at the same blistering speed as before.

The Z1 was my basic transportation in those days. My cars of the period were not always up to the job of getting me where I wanted to go. For a period I owned two sports cars: a 1957 MGA and a 1961 Sunbeam Alpine. Neither of these machines was a good example of their types. The MGA sported Volkswagen bumpers and turn signals, and suffered chronic low oil pressure. The Sunbeam looked OK, but was the victim of an engine transplant that left it with a Chevy fourbanger and three speed. On occasion I pressed my parent's Chrysler 300 into service if I really needed a car. For some period the Z1 even mounted a sissy bar (complete with peace symbol, I kid you not), that appendage making it possible to, with the liberal application of bungie cords, ferry home groceries.

Eventually I got around to taking the Z to the drag strip, which in this case was St. Louis International (now Gateway International) just outside East St. Louis. By that time the bike was about three years old and was closing in on 30,000 miles, but with the baffle pulled from the Yoshimura pipe and the air cleaner element removed, it did managed to turn a 12.7 110 MPH quarter mile. One of today's 600s could do that towing an Airstream, but in the 1970s that was good performance with a heavier rider who insisted on always using the clutch.

The primary impediment to consistent performance was the ignition system. Even when the bike was new, the stock breaker points and coils would only allow the 9,000 RPM red line to be exploited for a few hundred miles. After that, the plugs had to be removed and cleaned. My initial attempt to address this deficiency was to simply use better spark plugs. The best results were delivered by Champion Gold Palladium plugs, which at about $3 each were 4 times the cost of standard units. Even this extravagance was only a partial solution. It was obvious that the ignition system was seriously weak. It had been a disappointment that Kawasaki had neglected equip the Z1 with something better than the standard ignition technology of the day. They had blazed a trail with their capacitive discharge system introduced in 1969 on the H1 two stroke triple. That was one of the most significant improvements made in two stroke performance, and, in practical terms, and made the outright performance of that 500cc motor a really practical proposition. Almost as soon as the Z1 hit the streets, various vendors were offering kits to substitute some form of spark control other than the breaker points, but these all cost at least $100, and a component failure meant that even the local Kawasaki shop couldn't help you. Sometime in the latter part of the '70's Cycle magazine published a report comparing the relative strength of various motorcycle coils. It showed that, compared to even the most pedestrian American automotive coil, motorcycle coils were real weaklings. Apparently the coils themselves were the worst part of the system, and even breaker point systems could be made to perform at least adequately if provided decent coils. As a result of that article, suddenly everybody started putting $5 K-mart coils on their machines. Since I had long been in favor of using anything from department or hardware stores that could be pressed into service, I soon had four of the el cheapo coils lodged under my tank, and was using GM points and condensers, to boot. I used a dwell meter to set my timing. This was a big improvement, but, with the wide-spread adoption of electronic ignition by the automotive industry, I felt that an even better cheap but effective solution was at hand. I found it by adapting the first automotive original equipment breakerless system, the Chrysler ignition that appeared in the early 1970s.

In adapting the Chrysler ignition I decided to also use an automotive-style distributor - well, kind of. I left the triggering mechanism mounted on the end of the crank, as opposed to relocating it to the new distributor. I mounted a rotor and distributor cap on the right end of the exhaust cam. This was accomplished by welding a steel rod onto the camshaft and fabricating a mounting plate for the distributor cap, secured by the two outer camcover bolts. I cut a semi-circular hole into the camcover to accommodate the seal, which was fashioned from a rubber gas-tank mount and valve seals. The finished product looked somewhat crude upon close examination, but functioned as planned, distributing sparks from the K-mart coil to the four plugs for many thousands of miles. The Chrysler rotor and pickup were mounted in the place formerly occupied by the ignition cam and points, initially along with the stock advancer unit. I later decided to forego the advancer, which let me take a half inch off that side of the engine. The Chrysler ignition had a built-in ignition advance unit which was probably all wrong for the Kaw, but then the spring-and-weight advancers were never exactly precise units, anyway.

Since the Z1 was my primary means of personal transportation, truly radical engine modifications were not overly tempting. I did elongate the holes in the intake cam sprocket, to allow for the timing to be advanced slightly, and I bored the carbs. The latter was, in retrospect, a much bigger project than I had imagined. The stock carbs were nominally 28mm. At the time the hot setup was 29mm "smoothbore" carbs. These carbs were distinguished primarily by virtue of their slide design, which eschewed the common Japanese practice of using a slide with an open bottom. The smoothbores had closed-bottomed slides which resulted in less turbulence and greater flow. I couldn't easily convert standard carbs to this smoothbore design, but I could increase the flow by merely increasing the size of the throat, which I proceeded to do in the crude fashion permitted by the meager tools at hand. Using a screwdriver with a suitably sized handle and copious amounts of emery cloth, I hogged out the heavy, zinc-bodied carbs until they were about 30mm. The results in terms of performance were noticeable, but so too was the disappearance of a smooth idle. Changing the size of the carb throats had upset the fit of the slides, particularly when they were fully closed. The idle speed was several hundred RPM higher than the 1200 figure I liked, unless radical adjustments were made to the air bleed adjustments, which got the idle lower but also made it unacceptably erratic. But the top end power was nice. Eventually, however, I tired of the nuisance of a motor that couldn't be made to idle, particularly since I still insisted on running without an electric starter. I obtained a set of later model stock carbs, regrettably in the wimpy 26mm size, and economized on adrenaline.

Handling improvements were what the Z1 really needed, and so I set myself to that task, particularly after getting trounced by friends with better handling machines (relative riding skills being something I tried not to think about). The first changes any Z1 rider made back in those days were shocks and swingarm bushings, which I did. Original equipment shocks on seemingly all Japanese machinery in those days was pretty atrocious, especially when compared with the quality of the machines in other areas. This deficiency made for a thriving aftermarket. I chose probably the most popular make, Boge Mulholland. Next came tires. The Z1 was fitted with the standard rims for a large bike of that vintage, which meant that recommended tire widths were only a maximum of 3.5" in front and 4.25 at the rear. After going through a Goodyear rear tire, I decided to try one of the big 5" tires that were becoming available. I found a 5.10 X 18 Chen Sheng made into the pattern of an old Dunlop K-70. It was a pretty cheap tire, with little sidewall strength and generally light construction, but the price was right and, once mounted, it sure looked like it meant business. Fitting that wide tire to the stock rim meant that the tire would be significantly taller than a standard unit, and that the inherent sidewall weakness would be exacerbated. This made for vague handling at higher speeds, but at the time my inclinations tended more toward drag racing. Ironically, I never was able to exploit the supposedly better grip of this larger tire at the drag strip, as by then my engine was getting tired and my times languished in the high twelves. To get lots of rubber on the road I would lower the tire pressure into the teens (lbs/sq. in.), which did help the launch, but made the bike feel like I was riding on snow as I went through the traps at over 100 MPH.

Drag racing was fun, but in street riding situations the handling deficiencies of the Z still demanded my attention. Fitting quality tires on wider rims laced with heavy duty spokes helped a little. The only effective solution would be the relatively radical frame surgery engaged in by the racers. At that time, in about 1982, the theories about rear suspension which had prevailed during the previous couple of decades were being radically revised. Yamaha had demonstrated the superiority of "monoshock" suspension on both dirtbikes and road racers. Rising rate suspensions using linkages were beginning to appear. Fitting the Kaw with any such designs was well beyond what I considered practical, but substantial improvements could still be made to the rear suspension by moving the upper shock mounts forward. This would at the same time make the frame effectively stiffer and allow for more wheel travel. This was accomplished by sectioning the subframe, removing a section of the tube running diagonally to the shock mounts, and removing the top tubes to which the seat was mounted and replacing them with shorter sections which joined the main frame loop at a lower point. In addition, about 1/2" was removed from the vertical portion of the rear frame loop to in effect rake the front end slightly, and the upper frame tubes were spread slightly, again in the interest of increased rigidity. Complementing these changes to the rear of the frame, the original neck gussets, whose cracking provided testimony to the frames flaccid nature, were torched off and replaced with beautiful steel tubing from an old bicycle someone had left out for the trashman. The under-tank area was given similar attention. Go-fast guys were also strengthening their swingarms, so I did likewise by welding on angle iron. It ended up looking like something out of the Caterpillar parts book, but it seemed to work.

This was Full Tilt Boogie. It owed much to '70s era cafe bikes such as Rickman specials and the Vetter Mystery Ship, but built to a budget. Instead of using a set of aftermarket rearset footpegs, the stock pegs were merely flipped upside down. Only one disk occupied the front wheel, but the sacrifice in braking power did also produce reduced unsprung weight and a better ride. Pecuniary considerations also dictated the retention of the rear drum brake. To simplify the rearward relocation of the brake pedal, the old rod-actuated brake was replaced by a dual-leading-shoe brake from the front of a Kaw 500 triple, operated via cable . The changes to the rear suspension worked out quite well, yielding a comfortable ride, yet, in concert with the other modifications, taming all of the Z1's obnoxious handling characteristics. Any resemblance to the stock machine had by now been totally obliterated. The Pacifico fairing resembled a Rickman unit, the gas tank was an aluminum English unit, manufacturer unknown, and the solo seat/tailpiece was a totally original inspiration that was fabricated in my back yard. But the 900 cc engine was still tired.

Full Tilt Boogie lasted from about 1983 to 1985, when it was retired in favor of a 1982 Honda Saber. It is about to be reborn, however. The new, improved version, Afrochine, should take to the streets sometime this year.