UL­TI­MATE PS BIKES

What a lucky lot we are. Revel in this ros­ter of the bikes that changed our lives

Practical Sportsbikes (UK) - - Contents - Words: PS

From the ’70s, to the ’80s, and yes, the ’90s too... the best bikes bar none of their time

The 1970s KAWASAKI Z1

By ig­nor­ing the con­ven­tions that pre­vi­ously dic­tated what big bikes were all about, Kawasaki set down a new set of rules and in so do­ing cre­ated the mod­ern sports­bike. In a fur­ther twist­ing of the re­ceived norms, we have Honda to thank for Kawasaki mak­ing the first marker in the bat­tle for su­per­bike supremacy that pro­pelled ma­chine de­vel­op­ment in the 1970s.

When Honda launched the CB750 at thetokyo Show in Oc­to­ber 1968, Kawasaki were al­ready well down the line with a 750 sohc in­line four of their own. Kawasaki im­me­di­ately aban­doned what would have surely have been seen as a copy of the Honda and went back to the draw­ing board to pro­duce a big­ger, bet­ter in­line-four with two camshafts in­stead of a sin­gle knocker.

Ben Ina­mura was chief project en­gi­neer on the aborted 750 project and he got a sec­ond tilt at bik­ing his­tory when ap­pointed head of Z1 de­sign. In the au­tumn of 1972 he de­liv­ered the goods. al­though the Z1 project had been con­ceived as a bal­ance be­tween per­for­mance and us­abil­ity, its 82bhp en­gine (around 15bhp more than Honda’s CB750 could claim) was the real head­line grab­ber.

The 903cc Z1 didn’t fit any pre-ex­ist­ing ca­pac­ity class and its square bore and stroke mea­sure­ments (66 x 66mm) broke away from the ac­cepted wis­dom on how a big-bore bike should work. Like­wise, the pressed-up roller bear­ing crank owed more to Kawasaki’s two-stroke her­itage than to the CB750’S car-type plain bear­ing crank.and, to ap­pease the grow­ing eco-lobby, the Z1 pi­o­neered the sep­a­ra­tion of oil mist from the crank­case breather, rout­ing it into the air­box. Kawasaki claimed that this re­duced hy­dro­car­bon emis­sions by 40 per cent.

The de­sign of the Z1’s en­gine was un­con­strained by prece­dent but it in­formed a lot of the his­tory to come.

“Kawasaki im­me­di­ately aban­doned what would surely have been seen as a copy of the Honda”

| Pic­tures: Bauer ar­chive

1972

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