Kawasaki GPZ400 and ZX-4

A couple of my mates were running these old Kawasaki imports, buzzing away at the ubiquitous 600's that most of us rode. And not being far off the pace! After a heavy smash that wrote off my 600, I made an offer for the GPZ400R. The bike was as Kawasaki intended except for a rather loud 4-1, jet kit and modified electronic ignition. The stocker was limited to about 60 horses but these mod's allowed the watercooled four cylinder engine to rev deep into the red. The top speed of 135mph indicated about 75 horses on tap! For a thousand notes it was a damn good deal...

Or so I thought. So happened that the first day of ownership, summer turned into autumn with a massive amount of rain! The GPZ ran these relatively thin sixteen inch wheels shod with Japlops of a questionable age! Not a combination made in heaven. Any right wrist madness had the back wheel skipping and hopping all over the slippery tarmac and the front wheel felt very edgy.

This was because it had almost no adhesive qualities! I found this out the hard way after slamming the bike through a gap in the cages on a roundabout. I went to flick the bike up, making with the throttle, hoping to beat all the cages into the exit lane. I must've hit the throttle before the bike was completely upright, the front wheel flipping sideways.

My next conscious moment, landing on my knee and elbow as the bike skidded along the tarmac into the gutter. I managed to roll with my body's momentum, somehow just missing being run down by the cagers who must've thought they were tripping in a parallel universe! Both bike and I landed up at the junction of the roundabout and exit lane, the cars streaming past regardless.

After a quick look at my knee and leg flexing session to ensure nothing was actually broken, I pulled the GPZ upright. A cracked fairing, broken indicator, bent lever and realigned handlebar. Still rideable, so I blew into Reading, bought some cream for the gravel rash knee and made it home in one piece... never going over 25mph! I wasn't sure if the wobbling front end was a bent frame or wheel, or just me having a fit of the shakes.

Must've been the latter, because after I fixed the damage, the bike ran as true as before. Which isn't on rails, to use a well worn cliche, the sixteen inch front wheel always feeling a touch nervous but the upside was not much effort needed to heel it in and out of the tighter corners. Accelerate hard, though, the whole front end went light and the back squirmed all over the shop. Not a combination to experience when heeled right over on the edge of the tyres. Soon became obvious why the previous owner had been a cut and thrust artist of a high order!


Although the engine was a revvy old beast, not feeling happy until at least seven grand was on the clock, even in top gear the burst of acceleration between 90 and 125mph was pretty startling for a mere 400. As was the amount of exhaust noise it made, a lovely gravelly wail at twelve grand that used to make the hair on my back stand up.

Below seven grand there wasn't a clean flow of power, often some stuttering. This may just've been the non-standard components not interacting a hundred percent, but I did talk to another owner running a standard set-up who reckoned his was also a dull boy at low rpm. At higher revs the 29000 mile old engine felt like it was in peak condition, emphasized by the way the whole plot smoothed out!

The twin front discs had recently been upgraded to GPZ600 spec with decent stuff from the beakers. If anything, they were too powerful, just a single finger caress had the tyre smoking and the bars shaking furiously in my hands! No fun at all in the wet, tended to rely on shutting the throttle. Produced strong engine braking, along with lots of churning in the transmission and popping from the exhaust. Sounded like the whole bike was falling apart but it didn't actually seem to do any damage.

The rear disc barely worked, crud thrown off by the back wheel always found its way into the caliper, so old that it really needed a strip and clean every week but only got one every other month! Occasionally it would remember its purpose in life, locked on solidly, the back wheel snaking a good foot to either side of the bike. Sometimes it stayed on until given a good kicking!

The lack of mudguarding meant that all the nooks and crannies were soon filled up with road debris, once a little rot got under the paint or alloy it spread like wild fire. Had great chunks of frame paint fall off! With the full fairing most of the damage was hidden away, but the plastic itself was fast going off. Crazing and minor cracks were added to the red shade going very dull.

After a couple of months, the rust spread to the matt black exhaust, which then cracked up where the down-pipes joined up. What little baffling it'd been manufactured with was long gone. Even the tickover caused dustbin lids to bounce up and down, an unlikely chorus. Taking the exhaust off, two of the header bolts in the cylinder head snapped off! The threads were corroded solidly into the head! Bloody Jap alloy! As per the UMG's hacking rules, I drilled into the screws and cut a smaller thread in each. Worked okay!

The 4-1 was welded up, refitted with a proper silencer, off a GPZ600. This was a bit noisier than standard, prone itself to the good old corrosion blues. The carburation was way out! Lots of surging at low revs and it didn't want to go beyond eleven grand. The breaker gave me a collection of jets to play around with and after much messing with the four carb's I finally got back to where I started, though top speed was down to a mere 130mph. Fuel remained the same, around the 50mpg mark.

By 36000 miles, the engine rattles reverberated through the plastic! The camchain was on the way out! This was replaced by threading a new one on to the old, running it through the engine. Less of a hassle than a full engine strip. The valves and carbs were done, the first time I - or anyone else, probably - had touched them. The motor was a lot quieter but didn't give out any extra power.

A few months later there were a lot of electrical problems, traced to one of the alternator's coils shorting out. An exchange alternator and a bit of rewiring solved that. The handlebar switches were all very vague, so they were swapped for something more modern. A brand new battery was finally added, the old one looked like it'd been there from the time of the bike's creation!

Up to 40,000 miles, performance began to lose its edge. Worn out? Given the way it was run into the red most of the time, quite probably. Time to sell. The bike went for 750 notes. I added another 500 to the pile and bought a ZX-4 from another so-called friend which I'd been lusting after for a long time!

This can be considered as a more modern version of the GPZ, not much difference in power but the handling way ahead of the older bike. As it was both newer and much lower mileage (12,300 miles at the time of purchase), it's a bit unfair to compare it to the GPZ but I felt immediately elevated to a new plane of sophistication and could throw the bike around like a real hero rather than a suicidal arsehole.

Incidentally, the new GPZ owner stuffed the bike into a brick wall on slightly wet tarmac. I'd told him to watch out for the front tyre and fierce brake but he hadn't paid much attention to my mutterings. Weird chap insisted on fitting the GPZ's engine into a GPz750 chassis, having previously managed the rare feat of getting that engine's con-rods to poke out of the crankcase! Sounded like a real abortion but it's actually bloody fast and handles much better than the stocker! Kawasaki obviously missed an opportunity there.

One of the things I really like about the ZX-4, it fits me perfectly, whereas the GPZ had my knees and arms slightly misaligned and despite having a better saddle was less comfortable after the first 100 miles. The riding position on the ZX was still racy, felt much better at 120mph than it did at 20mph but, for some reason, it just suited me fine. Half the battle won!

It may just've been that, on expensive Metz's, the newer Kawasaki felt much more secure on the road - better than my CBR! - providing a much more relaxed time. I never had to wonder if the front tyre was going to go all wanton or if the back was going to shake itself to a premature death! The Kawasaki just did its job with remarkable elan.

Top speed was 140mph on the clock but this seemed somewhat optimistic as my friends' 600's had a slightly easier time of losing me than when I was on the GPZ! The ZX ran a stock exhaust which was so quiet I kept thinking the engine had stalled! However, acceleration from 70 to 120mph was a touch stronger, combined with its ease of handling, made for a much faster tool on the back roads.

Fuel was slightly poorer at 45mpg, though restrained riding could turn in a remarkable 65mpg (the GPZ didn't vary much) - restrained as in keeping the revs below five grand, the engine much smoother running and more contented than the GPZ. Oddly, the bars trembled slightly at the ton, where the older bike went really smooth, before the ZX's vibes disappeared again.

The price paid for the excellent handling and stability (I could go about twice as fast in the wet and still feel twice as safe) was poor tyre life, around 3500 miles a set. Brake pads did around 10,000 miles on both machines, the ZX actually having a rear disc that worked! For some reason it was much less sensitive to road crud whereas the front calipers gummed up after a month of winter riding. They were easy enough to clean up.

Some long, fast Continental blasting tested out the ZX's capabilities thoroughly. The bike wasn't fazed by constant 125mph cruising, held steady when the wind was whipped up into a frenzy by passing Merc's on the autobahn and generally gave off an air of quality and sophistication that was so lacking in the GPZ.

The first winter months somewhat gave the lie to that theory - wheels, brakes and exhaust rotting away at a rate that took my breath away! The easy low end power delivery was useful when the roads turned treacherous but I got caught on some diesel, went flying. After a certain point there's no way to snap the Kawasaki back into line.

The amount of damage resultant from the 35mph crash was incredible! Completely ruined the fairing, including the lights and indicators, cracked the front wheel, bent the forks, snapped off one handlebar, dented the tank and somehow detached the seat from the bike! Somehow, I'd escaped totally unscathed. In my darker moments I wish the bike had landed on me and saved itself from serious damage.

The frame was still straight, the plastic could be dumped, all that was really needed to get motive again, a replacement front end. Two hundred quid's worth of ZZR600 forks and wheel were bought from the breaker and fitted on. The bike looks rough, doesn't run so well and I've just gone off it! Have to sell soon.

Dave Crowther