PROJECT ZX990 TURBO

1990s WSB icon with 2019 WSB power, cour­tesy of a turbo. PS’S am­bi­tious/daft new project starts now. Tar­get 250bhp

Practical Sportsbikes (UK) - - Contents - Words: Chris New­big­ging | Pic­tures: Si­mon Lee

We take a manky ZX-7R and a tired GSX-R1000 to cre­ate a sav­age blown hy­brid

new project has been near the top of our pri­or­ity list: PB re­cently fin­ished its 2008 Fire­blade project with great suc­cess, and PS has taken a bit of a breather since its last big build. Time to get busy, and also make use of the com­bined knowl­edge now at hand. Mod­ern ex­per­tise with retro ap­peal.

So we scoured the small ads, browsed the web and drew in­spi­ra­tion from ev­ery source you’d ex­pect, be­fore the plan be­gan to form. A few year back, Scan­di­na­vian cus­tom shop Wrench Mon­kees slapped a ZX-7R fair­ing on a new Kawasaki H2 and called it a ‘build’. It was bob­bins: the fair­ing jarred with the size and layout of the mod­ern chas­sis. It looked what it was: tacked on. Same goes for a Z900 naked re­cently dressed up like a ZXR750 H1 – a lit­tle bet­ter fin­ished, but an un­suc­cess­ful mar­riage of retro ap­peal and mod­ern parts. But not a bad con­cept…

The ZX-7R is a PS favourite: a chas­sis with good fun­da­men­tals and time­lessly cool styling: you can’t go wrong with a 7R in these re­spects. But they were al­ways heavy, and the mo­tor de­served some de­vel­op­ment, but never got it. They’re also cheaply built, and only the most cher­ished of them last well.

Ours is not cher­ished. It is a minger. It cost us £1400, as val­ues are rea­son­ably strong and any­thing around or be­low a grand was ei­ther in­com­plete, dam­aged or hooky. Or a com­bi­na­tion of all three. This seemed the thresh­old for a com­plete start­ing point.

It’s a 1997 par­al­lel import, wear­ing all of its dis­played 49,000km (30,000 miles) and prob­a­bly more be­sides. It has been dropped: the fair­ing sides re­sprayed well, the top badly touched-up. The brakes are bind­ing on cheap wave discs fit­ted with irid­ium-ef­fect bolts. Poorly-touched-up paint barely hides the cor­ro­sion that blights the wheel rims and ex­haust. The ra­di­a­tor has chunks fall­ing off, the shock is goosed, and the choke doesn’t work. It might look OK in pics, but the more we looked the worse it got. But it’s all there, and straight. Some­thing to work from.

To give it 21st cen­tury ap­peal, it needs bet­ter run­ning gear and more power. Lots more. Over 100% more, in fact, we’re go­ing to tar­get Kawasaki’s su­per­charged ef­fort. No sense in even con­sid­er­ing the orig­i­nal en­gine. So it’s com­ing

out. The run­ning gear needs to do like­wise. At this point, the 2003 Suzuki GSX-R1000 in the pic­tures may be­gin to make a lit­tle sense…

A num­ber of ZX-10R pow­ered ZX-7RS ex­ist: a neat con­ver­sion on the face of it, giv­ing the over-en­gi­neered ZX-7R chas­sis the sort of power it was meant to han­dle as a WSB racer. But the en­gine it­self is an awk­ward lump with com­pletely dif­fer­ent en­gine mounts. There are off the shelfk­its avail­able, but they’re a bit Heath Robin­son. The best con­ver­sions in­volve some com­pro­mise.

A less pop­u­lar con­ver­sion, for rea­sons of brand al­le­giance we as­sume, is an early GSX-R1000 en­gine. It re­quires less cut­ting, and the en­gine mounts are in very sim­i­lar places, so the load on the chas­sis is closer to what Kawasaki in­tended. It’s also lighter than stock, with 150bhp or so as stan­dard. And it’s a bet­ter start point for the ic­ing on our green and blue Bat­ten­berg: the GSX-R lump is a glee­ful re­cip­i­ent of a turbo…

Forced in­duc­tion was the de­tail that sold us on this course of mad­ness – we can ex­pect any­thing be­tween 200-250bhp even with mod­est boost. That at least puts it on equal foot­ing with the H2 – pos­si­bly bet­ter off. It’ll tick the ‘mod­ern per­for­mance’ box, while keep­ing some of the best lines ever cre­ated by a Ja­panese man­u­fac­turer.

We’ve picked up a com­plete GSX-R1000 K3: ti­dier and lower miles than the ZX-7R (19,000 miles), and a top buy at £2650. It also shows signs of a mi­nor drop: bent gear lever, grazed crash bung, and a coat of white on the seat unit where it should be blue: prob­a­bly a par­tial re­paint to cover light dam­age.

We chose this route as buy­ing a mo­tor, throt­tle

“WE CAN EX­PECT ANY­THING BE­TWEEN 200-250BHP EVEN WITH MOD­EST BOOST. THAT PUTS IT ON EQUAL FOOT­ING WITH THE H2 – POS­SI­BLY BET­TER”

Clockwise from top: we’ll be hav­ing that en­gine thank you. Nasty, nasty hug­ger. ZX-7R min­gin’ be­neath the plas­tics. And pretty grotty all over if truth be told. Good ones are rare these days

bod­ies, loom and elec­tri­cal parts would cost al­most the same. It’s less has­sle and less cost in the long run, es­pe­cially when we sell the left­overs from both to re­plen­ish the cof­fers (and clear lockup space). We’re not go­ing to be miss­ing any­thing, as can be the way when you start with in­com­plete bikes or parts.. It also comes with a good set of mod­ern forks and brakes – we may well use those, too.

A pre­lim­i­nary mea­sure-up con­firms what the in­ter­net told us: the two mo­tors are roughly the same size, the en­gine mounts not far apart. The fab­ri­ca­tion job there shouldn’t be too dif­fi­cult, or in­volve com­pro­mis­ing the main chas­sis in the way the ZX-10R con­ver­sions do – drilling into cast­ings, cut­ting lumps from frame spars and the like. It would ap­pear that our work in­volves only the out­ly­ing brack­etry.

Pack­ag­ing cool­ers and the turbo it­self shouldn’t be too prob­lem­atic within the gen­er­ous con­fines of the Kawasaki fair­ing (when we’ve picked a turbo ex­pert to help us with that end of things. We may use the Suzuki forks, and a ZX-10R swingarm might have to go in to add a lit­tle wheel­base, just for grip and wheelie con­trol rea­sons. The H2 has a suite of rider aids to stop things get­ting nasty: not an op­tion open to us, so we’ll need to cre­ate as much me­chan­i­cal grip and chas­sis con­trol as we can…

We’ll be gut­ting the pair of them next month and start­ing the job of mar­ry­ing the best of the ZX-7R with more mod­ern per­for­mance. Though we’ll need to do some clean­ing first: fir­ing the GSX-R up to move it about, we were sud­denly en­veloped in a cloud of smoke as lube spewed from the oil fil­ter O-ring over the head­ers. En­gine off, spill kit out. The fil­ter wasn’t even fin­ger tight. Ap­par­ently the re­cent ser­vices have been car­ried out by ‘a mate who used to work in a Suzuki dealer’. If that’s the truth, I think I know why he no longer works for them… We’ll be check­ing the mo­tor’s ap­par­ent in­tegrity be­fore it gets large amounts of pres­surised air-fuel stuffed through it then.

Still, that’s noth­ing: then there’ll be a fair amount of fab­ri­ca­tion work, plus adapt­ing the Suzuki elec­tri­cal and coolant sys­tems to fit the Kawasaki chas­sis, then sourc­ing and fit­ting bet­ter run­ning gear, a turbo, set-up, re­paint­ing the whole lot, get­ting it to han­dle…

NEXT MONTH:

We of­fer up the GSX-R1000 en­gine and see just how we’re go­ing to make it sit tight and right

Two donor bikes and three or­gan donors

Tape mea­sure one of the few tools they can wield with com­pe­tence

Cur­sory mea­sure­ments sug­gest GSX-R thou lump will breeze in

If you’re af­ter some nice GSX-R bits, we can help

Suzuki shat its oil when fil­ter spun off on start-up. Won­der­ful

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