Kawasaki H1 Mach III, Fast But Feral !

Back in 1969 the Kawasaki H1 (aka Mach III) certainly was big news. Not the biggest news because it arrived at just the same time as Honda’s CB750 and without a doubt a 750-4 trumped a 500-3, at least in terms of magazine headlines.

However, there was no denying that a 60hp motor in a 174kg chassis was a potent brew – offering a better power-to-weight ratio than the Honda. In fact it blew the Honda off the road – or at least the drag strip, being good for a sub 13-second quarter mile, better than the CB750 by around half a second, while matching the top end of around 115-120 mph. If you could keep it out of the hedges – not an easy task – it was a giant slayer.

Kawasaki – who’d only stepped into motorcycle production seriously in 1959 (when they established their works at Akashi, then acquired rival Meguro) – came to the H1 via the A1 and A7 (that’s the 250cc Samurai and 350cc Avenger) twin-cylinder roadsters. These two had similarly been the proverbial bluetouch paper, but unlike the triple were disc-valve motors – as was being used on Kawasaki’s twin-cylinder then V4 grand prix 125cc road racers.

With all the Japanese manufacturers stepping up the capacity categories in the late 1960s, the Kawasaki H1 was effectively Kawasaki’s first "big bike", or high performance big bike at least, the earlier W1 650cc twin – based on BSA’s 650cc A7 – being a little, well, flaccid. But if the W1 was leisurely, the Kawasaki H1 was simply manic. Kawasaki, like Suzuki, had considered upsizing their twins to 500cc – and if that had been the case they would have kept the disc-valve induction, but their project engineer, Yukio Otsuki, also investigated the triple option – and liked what he saw. With a 120º crank the triple was better balanced than a twin and with three pistons the engine was pumping less torque through each of the cylinders which meant a lighter clutch and transmission could be used. Of course the layout meant forgoing the disc-valve induction, but even with conventional piston-port induction the power was impressive.

Some tech was still pulled from the GP programme, like the pointless electronic ignition (that had been installed on the KR3 V4 125) which was the first time electronic ignition had been used on a production road bike. At least it was used in the US, apparently in the UK the ignition could play havoc with your Radio Rentals TV set so standard points ignition was spec’d for the UK bikes until the H1D model in 1973. The Kawasaki H1 triple was a short-stroke, 60 x 58.5mm, with the cylinders inclined forwards by 15º. The finned, alloy cylinders held cast iron sleeves which featured a higher than normal silicon content to allow race-type two-ring pistons. The intakes and transfer ports were quite large but the timing remained road-bike safe.

Three Mikuni VM28SC carbs fed the go-juice. Width remained an issue as the ignition hung off one end of the crank while the alternator hung off the other. Straight cut primary gears and an alloy clutch again speaks of racer heritage – and intentions – but the gearbox was Kawasaki’s quirky neutral at the bottom layout (neutral being found underneath first, not between first and second as is usual).

Chassis design, by Tom Tagashi, followed the double cradle design that had held sway as design-optimum since Rex and Cromie McCandless’s first featherbed Manx Norton. However given the width of the crankcases Tagashi was forced to mount the engine high to maintain decent ground clearance, and this, combined with a short wheelbase (1400mm), would give the Kawasaki H1 its "exciting" handling characteristics. With 57% of the bike’s weight being transferred through the rear wheel – before you add a rider and a big handful of throttle – it’s no wonder the Kawasaki H1 got lively. Braking was taken care of by a 206mm twin-leading-shoe drum up front and single-leading-shoe at the rear. Newly developed Dunlop K77s did their best to keep the Kawasaki H1 rubber-side down.

Styling was by Ken Tada and while the Kawasaki H1 is ostensibly a conventional roadster he applied a few twists that certainly raised the bike’s profile, not least the distinctive fuel tank with negative panels for the riders knees, known as ‘eguri’ style – not that we can find a translation for that.

The Kawasaki H1 didn’t disappoint. 60hp from a 500 corresponds to a seriously heady 120hp per litre, considerably higher than the CB750’s ratio of 89hp/litre – and centuries ahead of Triumph’s 500cc T100 of the same year that was pumping at best 41hp. Given the 174kg dry weight this made possible a truly scintillating 12.80-second quarter-mile (when tested by the American magazine Cycle in early 1969). With that time being over two-seconds quicker than the old Trumpet you can see how performance like this really nailed the lid on the coffin for the Brit bike producers. Kawasaki would effortlessly prove the H1’s build quality too, stealing not just an amazing second place in the 1969 Bol d’Or 24-hour race, but picking up third and fourth too.

The Kawasaki H1’s performance couldn’t be questioned and with a very attractive price – it was way cheaper than the CB750 – it was a runaway success. Apparently 110,000 were made over the eight years of production (which compares with the 20,000 Z1300s made in nearly 10 years). Like all such period two-strokes it was the emission laws that finally defeated it. The H1 hung in there until 1975, then for 1976 Kawasaki gave it one last go, renamed as the KH500, but with emissions restrictions strangling the power to 52hp and with all the added weight it was a shadow of its former self.

The Kawasaki H1 is a blue chip classic, all day long. That goes for the first H1, but from H1A to H1F it’s still all-good and they’re all bankable as the Kawasaki triples do seem to be riding something of a wave of increasing popularity.

It was a proverbial game changer in its day and between the H1R and H2R the Kawasaki triples (alongside the Suzuki TR750 triple) did much to change the face of racing in the 1970s. That gives the Kawasaki H1 even more credibility. And finally, for a Jap classic it’s got a shed load of street presence. Viewed by anyone from a VJMC rivet counter to the Xbox-addicted snot-next-door you’re going to get pretty much the same reaction – respect.

Kawasaki H1 Mach III Specs

Engine: 2-Stroke, Inline-Triple (3-Cylinder), Piston-Port, Air Cooled

Bore x Stroke : 60 x 58,5 mm

Displacement : 498 cc

Compression Ratio : 6,8 : 1

Fuel Supply : 3 x Carburetor Mikuni VM28SC

Transmission : 5-Speed

Max Power : 60 HP @ 7.500 RPM

Max Torque : 57,3 N.m @ 7.000 RPM

Wheelbase : 1.400 mm

Dry weight : 174 Kg

Fuel tank capacity : 15 Litres

Frame: Double Tubular-Steel Cradle

Front Suspension : Telescopic Fork

Rear Suspension : Dual shocks, Swing arm

Front Brakes : 200 mm Drum Brake

Rear Brakes : 180 mm Drum Brake

Front Tires : 3.25 - 19 Inch

Rear Tires : 4.00 - 18 Inch