Beware the Jabberwock

…my son, or so the poem goes, though we doubt whether even Lewis Carroll had a 141bhp brute like this in mind when he wrote about Alice.

There are many different ways to buy performance, but power always costs roughly the same, no matter how you get it. The only thing that's certain is that it's never cheap.
     This turbocharged Katana is a classic attempt at raw horsepower; a typically American approach, using many parts which have been developed on the drag strip. In one way it's an interesting exercise in where power comes from (and where power goes to ... as witnessed by a small pile of molten pistons).
     It's also an indicator of what performance costs. It seems that if you want a street legal bike which will run quarters comfortably inside the ten second bracket you're going to need four or five thousand notes of the realm. You can then buy a GSX-R1100 straight out of the showroom. Or you could build a light, compact special like the Kawasaki Turbo Harris featured in our February issue. Or you could take a fairly fat and heavy first generation superbike, and make it even bigger.
     Gary Westerby took an 1100 Katana and the third option; the result is a motor that gives at least 140bhp, runs an easy 10.8 second quarter mile and pulls wheelies in third.
     We say "at least" 140bhp because when we saw that on the dyno, there was still more to come. In the same way, it would shave many tenths off the quarter mile time if the rampant output could be translated into forward - not upward-motion. Top speed, like the dyno figure, is academic with a turbo capable of delivering 20 psi boost or more, you can turn up as much power as you want. In the end, all you can measure is the melting point of forging alloys.
     Top speed requires an exercise in streamlining, gearing and high speed stability; the Katana sacrifices nothing to these particular gods.
     It was coming out of the quarters at 136mph, having just peaked in fourth. It began to go unstable at about 140mph but it was debatable whether the engine would take full boost for long enough to reach maximum speed, regardless of whether the rider could - or would - keep hold of the flapping handlebars.
     Gary’s quest for this kind of muscle took him to Towcester Tuning Shop, specialists in big bike power extraction and importers of much American hardware. They started with an 1170 Wiseco big bore job and added a Mr Turbo kit. This contains a Rajay turbine, plus everything that is needed tot fit it and feed oil to it.
     The kit is actually supplied for the 1100E - not the Katana - and TTS had to modify the exhaust tailpipe and make up a bracket to mount the boost guage. Fuel is supplied from a single, 38mm Keihin which Mr Turbo modify by removing the choke plate and adding an enrichment device instead.
     The motor then has to be modified to pump oil to the turbine and give it enough strength to cope with the new load. Vance & Hines high ratio oil pump gears were fitted to uprate the capacity (the roller bearing crank doesn’t cause any pressure build-up, so all that happens is the extra oil flow is diverted to the turbine).
     This feed is taken from an adapter (supplied in the kit) for the oil pressure warning light sensor, which comes from the main gallery. The return route goes via another adapter to the oil filler cap, above the clutch. An SF classification oil is used.
     The crankshaft was TIG welded by TTS (later versions have the mains welded at the factory, later still versions have all the pins welded to the webs). The rods and bearings are all stock, but heavy duty cylinder studs are essential. Here TTS use a variety of materials, depending largely on demand and availability, but EN16T, EN19T or 8120 steels are possible options.
     The stock cams, valves and guides are used, with Orient Express slotted sprockets so that the cam timing can be re-dialled. Peak lift on the intake cam is phased at 106 degrees ATDC, compared to the stock 110 degrees, the exhaust is phased at 114 degrees, instead of 110.
     Heavy duty valve springs - another Orient Express item- are used, partly because of the high boost pressure available and partly because of the motor's likely acceleration in the event of a missed gear, etc.
     TTS have flowed the head, but left a rough finish on the intake track in order to help fuel atomization and distribution as much as possible.
     The final beef-up work went into the clutch, initially with TTS backplate, and cush springs and latterly with the addition of an MRE lock-up clutch.
     Compression is 9:1- which is a bit high for anything other than racing, but it does mean there is no appreciable turbo lag. With this and the new cam timing, the unboosted motor probably has more midrange than a stock Katana. It certainly cracks off the line as hard as any other 1100 and boost appears in first gear, if you can work you hands and feet fast enough to make use of it.
     The first time we ran the bike, on the dyno, the wastegate was set to give boost around 20 psi. With stock ignition timing, the motor was detonating badly above 7000 and the high boost became something of a mismatch with the engine at maximum speed producing a power curve that just wanted to go straight up. We called a halt at 141bhp before the engine decided to scatter itself all over the test house.
     It still picked up on one piston due to a faulty taper on the skirt and, after a rebuild back at TTS, we took it to MIRA. One half-throttle pass showed how quickly it would get up to 140; it also showed that the single strut swing arm and the 16-inch front wheel made something of a negative contribution to high speed stability. It was never put to the test. Half way through the next pass, wide-open, shifting up at 8000 and getting something over 20 psi on the boost guage, I felt the power diminish. The only similar sensation I can recall is when a racing two-stroke melts a piston; you feel the edge go off the power and hear the crackle go out of the exhaust and you have about half a second left. Half a second was too much for pistons which were being fed one-and-a-half atmospheres of boost. By the time I’d hit the clutch and stopped, number 3 piston had gone, leaving the tell-tale trail of blue smoke drifting the length of the timing straight.
     Undeterred, TTS went back into the rebuild mode, this time with Cosworth pistons, Dyna ’S’ ignition retarded 2 degrees from stock, and the wastegate wound out as far as it would go. This would hopefully regulate the boose to 9 or 10 psi, which is the safe limit for sustained (i.e. longer than a drag strip) running.
     TTS have become distributors for Cosworth pistons which, although they are forged and stronger than the standard cast items, are not significantly heavier. They have a thicker piston pin, but this is kept shorter, avoiding a weight increase here. Even if the pistons had been heavier, it wouldn't have caused too much trouble because the motor was being kept below 8000rpm and rod or big end failure was not likely to be the engine's weak point. The strength to resist the huge thermal loading was the main requirement and TTS were hopeful that the new pistons would be up to the job.
     They have their own rings, which are interchangeable with Wiseco, and use conventional circlips. There is often a problem with tuned engines allowing the pin to fret against the clips, often resulting in the clip, breaking or coming out of its groove. Several alternatives have been tried, such as AE's spire lock or the PTFE buttons used in America.
     Tapered pins, which theoretically push the circlip harder into its groove have not always worked, because the fretting action opens up the groove and the clip then doesn't seat properly. TTS are experimenting with their own glass-reinforced PTFE buttons - which is probably the best solution so far, except for the cost of the American-made items.
     The rebuilt engine was ridden around on the road to bed in the new parts, suffered a couple of aborted photo-sessions when the weather turned nasty and was finally wheeled on to MIRA's tarmac for the acceleration runs.
     By this time the boost gauge had a tell-tale needle. We decided to cut our ambitions and restrict the bike to quarter-mile tests and the initial runs of around 11 seconds showed the boost still wasn't fully under control. The valve in the wastegate simply wasn't big enough and couldn't handle the gas flow. Boost peaked at 15psi and threatened to limit the engine's life to something in the order of seconds rather than minutes.
     Acceleration between 6000 and 8000 was nearly quicker than the gear selector took to reset itself. The Katana is a tall bike and, in drag strip terms; it has a short wheelbase, short enough to be turned upside down by 140bhp no matter how you spell it.
     Once it had left the line, boost was regulated by throttle position and was used mainly to keep the bike's nose within a few degrees of the horizon. Full throttle was something that happened in third gear and even then it lifted the wheel. Watching two instruments and the horizon at the same time proved to be an acquired art, not to say, an acquired taste, giving a best of 10.87s and 134.7mph. Given some means of using the bike's potential a little more effectively, there's no doubt it , would get a lot closer to the 9-second bracket. And there would be an added bonus. Running full load (for nine seconds instead of ten would put a big margin on the bike's reliability . . . TTS are at Unit 3, Bradford Close, Finedon Road Ind. Est, Wellingborough.

©Copyright 1986, EMAP Plc.

  This article is from the June '86 issue of Perfomance Bikes Magazine and is reproduced with the kind permission of EMAP Plc.  Many thanks also go to the keyboard player of the Bastards from Hell, without whom none of this would have been possible.