Kawasaki (K)Z1000J

Mastering the Zed

Remembering motorcycling’s greatest all time engines, what comes to mind? For this scribe, the Vincent appears for its beauty, any L-shaped Ducati for drama, BMW/Guzzi twins for traveling and a Zed-four in my fantasy Bol d’Or special. Discounting some standout modern designs, this writing focuses somewhere near 1972…the infancy of motorcycling’s golden age. Being absolutely dominate in all types of competition makes a convincing argument for the DOHC Kawasaki, but there’s far more to the Z-1’s role as a history changer than mere acceleration. How heavy is Kawasaki Industries? Making a graph to chart production Big-Four performance from 1969-forward, Kawasaki’s line lives at the top. Rarely for total production (that too may someday change) but specifically open class ranking. Somewhere, perhaps where the ships and trains were made existed a core that just knew how to build a proper motorcycle. Examples of their work can be found all throughout the following decades.

Credit for a large portion of my moto-education in tech and test bikes goes to tuner/restorer TJ Jackson. Those who know TJ and wife Pam certainly recognize the couple’s vast interests, and their collection of vintage exotics reflects that. Generous and direct, tapping into TJ’s service career has proved invaluable, and his knowledge as a business owner offers a ‘both-sides-of-the-coin’ approach. Breaking in with Kawasaki as a wrench, the brand remains TJ’s favorite and he’s really good at restoring them. Thanks to him I’d become a fan of all things Zed, and my study from the 903cc forward stopped at 1981’s Z1000J. An all star among the press when released, that research also turned up a vibrant 1000J enthusiast base. Be it past or present, all agree that nearly every aspect of performance was improved…this, despite widespread market variance of body/graphics. “You need a Kawasaki,” TJ recently texted, responding to some photos I’d sent of my torn apart Le Mans. “You know, something to ride when you’re working on the Italian stuff.”

Blueprint: 1981 Z1000J

One of the more interesting angles of 1981’s Z1000J were the number of issues seemingly working against it. Dominate for most of the 1970s and despite attempts to boost handling and spread power, Kawasaki had drifted behind Suzuki and other, select standouts by 1978. No longer the range leader, much of the development done for the new GPz1100 carried over. Kawasaki’s presentation of the Z1000 made clear the motorcycle division saw the Z1000 as a core priority. This perhaps, or almost certainly for those who simply refused to ride anything but a Z-1. Looking to regain the class lead in power and handling the bike needed to be lighter. In its profile you see this minimalist approach: stronger where it needs to be, lighter where it doesn’t. This formula wasn’t new, but Kawasaki’s mixing of it resulted in its best ever effort.            

Engine: Air-cooled, DOHC – 998cc – 2v per cylinder – 5-speed

Starting inside the engine reveals almost all new components. Yet, in a time when 4-valves per cylinder was trending, the 1000J 2v arrangement makes the engine feel more like a final revision of the original. Which in fact it was. Traditionally styled in classic Zed with square cam covers and mixing polish with paint, the major changes made to the 1000J’s crankcase came from eliminating the kick start mechanism. Pressed together, the crankshaft rides in 6 places (four inner mains and two outboard) with shaved ‘pork chop’ flywheels to spool more 903cc like. Applied as an update to the 1015cc unit, the oversized crankpins remain, but opened inside to shed weight. Toss in revised con-rods and the crankshaft alone lost 5-lbs. Now displacing 998cc via reduced (69.4 vs 70mm) bore, things get interesting when those same period testers claimed the 1000J’s tuning specs had their roots in AMA Superbike. Yoshimura perhaps? I’m thinking some important things were left out, but the camshafts are 5-degrees advanced (popularized by ‘degreeing’ previous Z1s) with lobes that use increased lift and duration/overlap. Intake and exhaust valve diameters (37/32mm) were the largest ever fitted by Kawasaki at that point. Speaking of bigger, the 1000J’s all-aluminum 34mm Mikunis replace the 1015’s 28mm carbs and fit into a new ‘reed-valve’ airbox. CDI ignition fires the mixture, and the (1981 anyway) compression ratio is a rather conservative 9.2:1. Driving the slick-shifting 5-speed, a hefty spur primary connects with an all alloy clutch basket fit with an extra friction plate.

(Nothing extraordinary, but nicely upscaled – built for increased performance and durability. Period cutaway shows original kick-start, 903cc engine, circa 1972. Both pressed up, 1015cc KZ crank (top, from Cycle) shows heavier, full-circle flywheels. Spares and aftermarket support remain outstanding.)

Chassis: Braced steel tube cradle – 38mm forks – twin shock rear suspension – cast wheels

On the road, Kawasaki’s chassis makeover had a greater impact on overall performance than its high-output engine. Carrying over improvements made to the similar looking Z1000/M.k. II frame, larger diameter, welded, thin-wall tubes are used at high stress areas and attachment points. As reported by Cycle, the 1000J’s steering head gusseting was first seen on KZ750, with bracing to tie the top main tube to the cradle and the front down tubes cross-braced in two places. These braces serve double duty, attaching and smoothing the engine with new rubber engine mounts. Earning rave reviews was the Kawasaki’s front end – now with beefy 38mm tubes in new, wider spaced (241mm) aluminum trees. Pulling off a neat trick that quickened steering and increased stability, a 1.5 degree reduction in steering head angle (27.5) worked with an increased trail figure of 12mm. To understand this weight bias revision better, the engine-to-rear-wheel distance remains the same, but engine to front wheel distance increased 1-inch. More unsprung weight was trimmed by reducing brake diameter to 236mm, but function was improved using flat rotors that bolt directly to the wheel hub. No cheap bushes here, for as the very best available Kawasaki fit tapered steering head bearings and caged needle rollers for the swingarm pivot. In total, the frame is 7-lbs lighter. Looking at every component for a chance to trim more poundage, plastic was used for the seat base, turn signals and battery box. A new main stand shaved yet another 5-lbs. “It’s a better sports bike than the GPz 1100,” write the editors at Cycle Guide. “Much smoother, more confident at speed and it absolutely rips from 6000 to the 8500 rpm redline.”

(First year 1981 Z1000J in blue. To the best of my knowledge, 1983’s ‘SS’ KZ1000J3 was the last civilian production year. More incomplete research says the black with red ‘1000’ graphics were available in Canada, Denmark and other Euro markets. Teardrop fuel tank on US import (in action at Cycle magazine) and GPz/Euro versions both hold 5.7 gallons. Note low handlebar, rear-set pegs/shorter control arms, all shared with the GPz1100B1) 

Period competition / press:

Pausing to consider 1981’s best superbikes, the list can get pretty long. Talking it over, TJ talked about the differences between Kawasaki’s period Zeds and more elemental, tightly focused Euro flyers like SS Desmos, Jota triples and the Moto Guzzi Le Mans. “These existed for a core of fringe riders,” said Jackson. “The reality being a good rider can ride anything quickly, the 1000J proved Kawasaki could do better. Still, in my experience, more riders just wanted a fast, good looking bike that didn’t leak oil and started every morning.” A good example of this mindset can be found in the 1000J’s protruding left-side alternator – moved behind the cylinders by period race tuners for cornering clearance. “Seeing as how the stands and exhaust touched first, Kawasaki reasoned it was silly to move it,” wrote Cycle’s editors in 1981. For production motorcycles, the gap between Japanese and Euro handling narrowed with Suzuki’s 4-stroke GS750 of 1976, but the CB750 and Z900 engines were well established in European Bol d’Or-type endurance racing. Honda continued development of its four (in RCB form) all through the 1970s, while the Z900 four not so quietly took over as THE engine of choice. Its ability to make power and reliably sustain it made the Z-1 a legend…the wailing exhaust and primary gear whine tossed in for free. For years following, special frame icons Egli, Moto Martin, Rickman and Harris wrapped their designs around the Z-1. Less flashy than the CBX’s glittering row of cylinders perhaps, but the Kawasaki is better when other priorities exist.

For the 1/4-mile crazy editors at Cycle, Cycle World and Cycle Guide, Suzuki’s 4v 1100 four lived at the top in 1981. To be fair, the big GS earned its place by mixing speed with real (lasting) stability, owner friendly ergos and maintenance, plus its own brand of mechanical ruggedness. Basically benefiting from the new GPz’s development with its slightly smaller, carbureted engine and uniquely fitted out, Kawasaki’s 1000J pushed for top honors in 1981. Weighing a full 30-lbs less than before, its 11.7 second quarter mile time trailed only the GS (11.18) and GPz (11.51) while posting nearly identical terminal speeds. The diet had paid off. Complaints were few – testers liked Kawasaki’s neutral finder but not the transmission’s first gear clunk, and the stock rear shocks were deemed insufficient. “It feels and sounds better than the Suzuki,’ wrote one tester. “Everyone wants to ride the 1000J.” “The old Zed is a slugger with a knockout punch,” wrote Cycle in October of 1981. “But the 1000J is a polished boxer with an even stronger right cross.” Concluding the 1000J shared 1981’s performance crown with the Suzuki 1100, the new Zed was summed up thusly; “Kawasaki peeled off the KZ label, stuck it on a whole new motorcycle and got the quickest and fastest one liter gun – and the best Z ever.”

1000J heritage – KZ1000R and Z1000-Police

Cycle’s editors in 1982 were quick to point out all the things Kawasaki’s 1000R Eddie Lawson Replica had in common with the J-model, but it’s a different motorcycle. New trees jack the rake to a “Ducati-esque” 29-degrees, with rock hard fork valving and equally stiff Showa piggybacks aimed at increasing stability into triple-digits. “Above 75-mph it all starts to make sense.” With all the factory GPz stuff (1100B fairing, tank, rearset controls, levers) it’s closer to the Euro 1000J than anything, and its AMA backstory adds tons more history and appeal. Sure, it looks the business, but that Kerker 4-into-1 means you’ll lose the mainstand, and it must be removed for oil changes. Does anyone care? Probably not, as the 1000 ELR might be the hottest Kawasaki collectible right now. Produced for world-wide export in Kawasaki’s Lincoln Nebraska plant, the 1000 Police fit floorboards, a fiberglass fairing, various boxes and other special bits over the original 998cc base of 1981. 34mm Mikuni carbs and all. The ultimate barometer of greatness? Nearly 25-years of continuous production demonstrates all one needs to know about Kawasaki’s 1000J. Nolan Woodbury