Alan Cathcart

2002 has seen a technical watershed in the evolution of the Supermono class, aka Sound of Singles, with the debut of the Tigcraft R0.5 Minimono - the first of a new generation of road racing singles powered by one of the high-revving, small(er)-capacity four-stroke motocross motors now dominating the Open MX class at world level.

In a fascinating standoff between little and large, the 445cc Minimono’s rider Mark George won this year’s British Supermono Water-cooled title and finished a close second to the fastest of the old generation of enduro-powered maxi-singles, the 780cc Gallina Suzuki ridden by Mark Lawes in the European championship. That included winning the most prestigious race in the European Supermono calendar at Assen in June, as well as scoring another upset victory at Brno in September, both times on big tracks which were expected to favour the bigger-engined bikes.

In an age when every form of racing, from Superbike and Supersport to MotoGP, is increasingly burdened by restrictive regulations as much aimed at telling you what you can’t do as what you can, the Supermono class stands out as the ultimate refuge of free-thinking non-conformity, inviting constructors to build a bike which embodies only the requirement that it should have a single-cylinder four-stroke engine. Otherwise, anything goes, and it can be no coincidence that John Britten, of all people, was hard at work on a six-valve single at the time of his tragic early death, or that Wolfgang Felber, before becoming KTM’s prolific chief engineer, a decade ago built and raced a KTM Single Racer with which he personally won the prestigious German championship. Engineers like classes such as BoTT/ProTwins or Supermono, formerly known as the Sound of Singles since its creation in Japan in the mid-’80s before coming to Germany in 1989, then swiftly expanding throughout Europe until it was adopted as a support class to the World Superbike championship in the mid-’90s - but such categories are not favoured by officialdom worldwide, for the simple reason there are no restrictive regulations which the likes of the FIM and its national federations can seek to enforce. This is no-strings, zero-bureaucracy racing in its purest form.

This explains why the only time the FIM tried to get in on the Supermono act and started tampering with the free-&-easy formula which had successfully fuelled the category’s climb to SBK support level, they messed things up. That’s what happened back in 1994, when for the Supermono support races held at World Superbike rounds, they introduced an arbitrary 110 kg. minimum weight limit in response to pressure from Ducati, whose desmoquattro Supermono had entered production the year before, and still remains the only customer SoS racer ever produced by a major manufacturer. However, because of its heavy eight-rocker dohc desmo cylinder head and complicated (but effective) articulate conrod anti-vibration system, La Ducatina was also rather heavy, and though I and my fellow ducatisti swept all before us in the bike’s debut season in 1993, we found it rather harder after that to compete with other leaner, lighter bikes which had the added advantage of increased capacity.

Realising that imposing a capacity ceiling was impractical, the Italian-dominated SBK/FIM technical legislators decided to help Ducati stay competitive by dreaming up a 110 kg. minimum weight limit - immediately negating the benefits delivered by 100-kilo hardware built around the small capacity motocross engines of that era from manufacturers like Husqvarna, Husaberg and KTM. Even though I was Ducati’s leading Supermono rider at the time, I complained about this in print as contrary to the whole ethos of the Supermono class, but to no avail - and anyway, it didn’t work: I finished runner-up in the European Championship both times I contested it on the Ducati - first to Tommy Korner’s Uno-Rotax (in spite of Ducati drafting in some support for the final round at Mugello, in the form of an unemployed 250GP rider called - Frankie Chili!), then in 1996 to the Over-Yamaha. No payoff.

The point of all this is not so much a walk down memory lane for yours truly (though I have to admit my Supermono racing days were among the most enjoyable I spent in a 25-year racing career), as to explain why until now, nobody yet built a lightweight, under-capacity Minimono - even though the new generation of light, compact off-road engines pioneered half a decade ago by Yamaha but now available from a host of manufacturers including KTM, Honda, Husaberg, Cannondale, Vertemati, Suzuki, VOR, Gas Gas, Husqvarna, TM etc. offers so much potential in this direction. But with the thriving Supermono class now self-administered at European and National level, as always in the USA and Japan, and no longer by the FIM, the minimum weight rule was chucked out some time ago - though it wasn’t until this year that the perspicaceous Dave Pearce of Tigcraft typically became the person to construct the bike everyone else had been wondering about building, without ever doing so. Having created exactly 100 customer Supermono racers over the past decade, mainly employing BMW, Rotax and XTZ660 Yamaha engines, as well as designing the frames for the factory MuZ racers and the BMW-engined Norton International road bikes, the British chassis specialist is the recognized guru of Supermono R&D, whose bikes continue to win races and titles around the world, from the USA to Europe, and even in Japan - so it was almost inevitable he’d be the one to build the first Minimono.

"I took a sabbatical from the motorcycle industry for a couple of years, but with the current resurgence of interest in Supermono racing thanks to the dedicated enthusiasm of its leading practitioners, I decided to build another bike - but I didn’t want it just to be a 21st-century version of what I constructed ten years ago," says Dave. "I’ve always believed that the route to building a better single is to cut down on weight and tyre widths, and with the refined suspension available from today’s 125cc GP racers, coupled with any of the new modern generation of small motocross engines, it seemed this would be an ideal combination to build a competitive bike. The fact that everyone else thought I was crazy made this a better idea - I lost count of the so-called experts who told me the engines weren’t made for road racing and would be chronically unreliable, or that we wouldn’t be able to get enough power out of them. It’s been very satisfying proving that in Supermono racing small can be beautiful, too - and the orders I’ve already received for replicas from customers in the USA and Japan, as well as here in Europe, shows there are others out there who’ve also seen the light!"

The R0.5 Minimono (half an R1 - geddit??) came together after a deal was brokered with Yamaha Europe to supply a YZ426 engine - the Japanese giant’s Euro-HQ in Amsterdam is full of people interested in Supermono racing, and the chance to see how the firm’s new generation of ground-breaking off-road four-strokes would perform on tarmac, has been an unanswered question many of them were eager to resolve. Dave Pearce initially planned to match this motor up with a TZ125 chassis sourced from his fomer race mechanic Katsuaki Umemoto, who today runs Tigcraft Japan - but opted instead to design his own Tigcraft tubular steel frame for the bike while retaining the Yamaha suspension, because of the vibration and extra stresses which a heavier, torquier fourstroke engine would impose on the 125 GP bike’s aluminium Deltabox chassis, typified by the fact that it broke the TZ125 cushdrive the first time they tried to bumpstart it! The result was completed towards the end of 2001, and began testing in the hands of the project’s first customer Phil Daw, but although the bike showed huge promise and worked well straight out of the box, says Pearce, its track debut was delayed because of his move the other side of the Channel to France, where Tigcraft is now established just an hour away from the Eurotunnel. But having opted to contest both European and British Supermono Championships in 2002, the Minimono has proven its potential, currently leading one title chase and running second in the other, maintaining a 50% batting average in race victories. The chance to test the bike at Mallory Park delivered an interesting look into what may well be the future of the Supermono category - made all the more poignant by the fact that in my pre-Ducati days, I actually used to own and race the Gallina Suzuki which is the R0.5’s main rival, even if the 135 kg. device certainly never delivered the 85 bhp at the rear wheel which it now churns out, when I sold it to current owner Chris Price!

That’s a lot more of everything than the Minimono, whose watercooled five-valve dohc engine with gear-driven counterbalancer has been tuned by Clayton Williams of Willpower, designated engine-builder for the Yamaha UK motocross team, to produce 56 bhp at the rear wheel at 10,800 rpm in the form I rode it - a significant increase from the stock motocrosser’s 42 bhp on the same dyno. "Originally we had 51.8 horsepower at 10,000 rpm in Supermono form," says Dave Pearce, "but that was still using the stock 426cc configuration. We then lengthened the stroke 3mm so that the engine now measures 445cc, with a 1.5mm longer Arrow steel conrod, stock piston with 11.5:1 compression, altered cam timing, and an all-new big-bore exhaust from London-based AC Exhausts, with a larger primary and very slow-taper megaphone. The result has more torque as well as better power than before - it’s an all-round improvement."

Willpower’s tuning work is focused on the cylinder head, which has been ported and flowed, then fitted with camshafts sourced from an American MX race kit, reground to deliver 1mm more lift - but it’s the cam timing which is the secret of the Minimono’s competitive power output, says Pearce. "The YZ426 MX racer and WR426 enduro have the same camshafts but vastly different power outputs, and this is why," he says. Stock valve sizes and springs are retained, but with the YZ426’s titanium valves replaced with stainless steel items from the same U.S. racekit, for enhanced reliability. The 5-speed transmission with oil-bath clutch is unchanged from stock, but the standard Yamaha self-generating ignition system has been enhanced with an Australian-developed programmable ECU supplied by Yamaha UK.

This potent little power unit, weighing just 29 kg. without its single 41mm Keihin flatslide carb (compared to 38 kg. for a BMW engine, 45 kg. for a Yamaha XRZ and an unbelievable 52 kg. for a Suzuki DR750!) sits in a compact Tigcraft twin-loop chassis delivering a mere 1220mm wheelbase, constructed from 4130 chrome-moly steel tubing and as on almost all Pearce’s frames, incorporating the oil tank for the dry-sump engine. Chassis geometry is the same as the TZ125 which inspired the bike, with a 22-degree head angle and just 82mm of trail from the 35mm Kayaba upside down forks, which retain the same springs as on the GP bike they’re sourced from, with only slightly stiffer damping settings. The GP racer’s aluminium swingarm is also retained, pivoting in the vertically-split engine cases and working a Dutch-made TechnoFlex shock via the stock TZ125 rising-rate link. "The shock is exactly as supplied for a 125 GP road racer, but with 25% more rebound damping, which we’ve found seems to suit big-pistoned singles better," says Dave Pearce. Fitted with RS125 Honda polycarb bodywork, but a special aluminium Tigcraft fuel tank reflecting the greater bulk of the four-stroke engine, the R0.5 Minimono weighs in at just 88 kg. with oil and water, but no fuel - a figure achieved without the use of any titanium, says Pearce, apart from the bolts securing the single 300mm front Braking petal disc, and its 185mm rear counterpart. "It’s important to stress that this is a very low-budget bike," says Dave. "We effectively have no carbon-fibre or titanium in it at all, and it’s been designed to readily accept the running gear from any Honda RS125R or Yamaha TZ125. I’m very concerned at the increased costs of the Supermono class, where building a competitive BMW-powered bike will cost the wrong side of £15,000. What I’ve proved here is that without too much power and employing a similar level of expertise to what a skilled customer can do at home, it’s possible to build a bike which will give you loads of fun and win races. We’re selling a Minimono frame kit for £2500 tax-free ($/Euro 3.750 - AC), which comprises the chassis and oil tank, plus a petrol tank to suit. Everything else can be sourced by the customer on a bolt-up basis - although we do offer the turnkey option of a ready-to-race replica of the R0.5 for between £8,000 and £10,000 ($/Euro12,500-16,000 - AC), depending on the specification." Sounds like mission accomplished in terms of lowering costs to enable the dedicated enthusiast to roll his own.

OK, but what’s it like to ride? Do you have to be a star midget to race a Minimono, or can more normal, non-125 GP-sized human beings hope to be competitive on such a bike? Recalling my own ongoing difficulties as a six-footer in squeezing aboard the 125 GP racers I’m invited to test, I was sceptical to say the least - even after noting that at 5’9"/1.75m, Mark George isn’t exactly minuscule in stature, even if he does weigh a mere 10 st./140 lbs./64 kg. soaking wet. That’s probably a much more important statistic than height in maxing out the Minimono’s performance, because much to my surprise while the little bike felt small and dinky to sit on, it wasn’t unduly cramped. Mark says it’s like an armchair compared to the RS125 Honda he used to race, and I’d agree with that - though only because he’s moved the footrests 60mm back and 20mm down compared to the TZ125 which the bike is based on, and has effectively raised the seat height by 25mm by fitting that much thicker a pad, which gives your legs extra space, plus it has the useful side-effect of throwing more of your body weight onto the front tyre, to enhance grip and help with keeping up turn speed. It’s a nice package, which although it’s very slim and toylike, so that I felt draped over the Minimono rather than ensconced in it, actually offered sufficient room for me to tuck down behind its narrow, domed screen down the Mallory straights, knees tucked in tight to the tiny fuel tank, gripping the steeply-dropped clipons in some semblance of an aerodynamnic stance, with the slipstream ducted over my shoulders by the flanks of the fairing wings.

It’s hard to over-emphasise how completely different the Minimono is to ride compared to the Gallina or another of the big 700cc-plus singles - though ironically it does share quite a lot in common in terms of technique and riding style with a Ducati Supermono. That’s because the key to redressing La Ducatina’s horsepower and weight disadvantages compared to the maxi-singles has always been to exploit its sweet handling and extreme 54/46% frontal weight bias (thanks to the horizontal cylinder’s heavy desmo head) to maintain corner speed and keep up momentum. The R0.5 has the same weight distribution, and asks you to ride it the same way, making the guff about the danger posed by conflicting lines through corners from little and large, spouted by advocates of re-establishing a weight limit, all the more ludicrous - if it exists at all, this has been a feature of Supermono racing ever since it started. So what else is new??

The Minimono endeared itself to me my allowing me to bumpstart it in the paddock - try doing that to a Ducati, and make sure you have the oxygen bottle standing by for when you finally give up - though you must be quick on the draw with your clutch hand since there’s so little inertia in the engine. This is very quiet at all times - Dave Pearce says that making it any louder loses 2 bhp! - and also very smooth: there’s absolutely no vibration even as the rpm mounts from a motor which feels punchy and potent as well as eager to rev - if, somewhat inevitably, not exactly muscular, so much as meaty and dependable. It drives cleanly out of the Mallory hairpin or chicane without using the clutch from 6000 rpm upwards, but strong power isn’t available until just over 8000 revs, when you can really feel the engine start to accelerate harder. However, there’s already 48 bhp on tap at 8500 rpm, before the 10,800 rpm/56 bhp peak, which means there’s an extremely flat power curve at high rpm which you must use the sweet-shifting race-pattern gearbox to keep dialled in - the engine’s apparently safe in motocross use to 12,500 rpm, but to respect the more sustained high rpm in road racing, Mark George says he usually shifts up around 11,500 revs. The choice of ratios in the stock 5-speed MX cluster suits this, with the bottom four gears very close together, producing a seamless surf of engine torque denoted by an exhaust note that, while still an unmistakeable gruff-sounding single, becomes higher pitched and more musical the closer you get to the five-figure zone. There’s a bigger 800 rpm gap to top gear, which won’t stop you searching for a non-existent sixth at first, though the Minimono is pretty long-legged, as proved by its Assen victory on a fast circuit with the crucial advantage of having lots of banked turns where you can keep up corner speed. Remember that 125 GP bikes corner faster than heavier and more powerful 250s and especially 500s, and you’ll understand where the Tigcraft R0.5 is coming from.

That’s the key to riding the Minimono hard, though it’s also easy to pick up time through a tight chicane like the Mallory one, because it steers so quickly. Though it’s extremely light-handling, it’s not nervous - just very nimble, sitting more securely on the road than a lighter 125 GP racer with the same build, thanks to the heavier engine. But the radical steering geometry by four-stroke standards (I reckon Erik Buell would approve of this bike, judging by his new generation of Firebolt V-twins!) means the R0.5 changes direction very fast, but still controllably - only you must be prepared for it to pop a six-inch power wheelie if you get hard on the throttle in second gear exiting the Mallory chicane when cranking it hard over for Devils Elbow, or again in fourth gear at 9000 rpm at the Esses. The Ohlins steering damper takes care of any aggro, but it pays to remember that this is a very short wheelbase bike with a lot of torque from the four-stroke motor. In spite of that, it rides bumps well thanks to the GP-level suspension package, coping well with the car-induced ripples exiting the Gerards sweeper, with no chatter anywhere, even under power. It did understeer noticeably there and exiting the Esses, though - but this is almost certainly a function of my, ahem, 35% greater body weight than the gossamer Mark George compressing the rear end unduly under acceleration. Still, it was easy to pull such a light bike back on line, and everywhere else it was super stable on the gas.

Not so much under heavy braking, though, where again the short wheelbase promotes undue weight transfer that will have the back wheel waving about in the air as you try to trail- brake into a turn. The trick here is to use the rear brake first, to promote squat before you then squeeze the front lever hard as well - it did take a while to judge distances and the single front disc’s stopping potential properly. Dave Pearce is absolutely right to opt for a single disc on such a light bike, not only for reduced unsprung weight but also for the lesser gyroscopic effect of a single disc speeding up the steering. However, that’s not to say it works as well as two, so you just have to dial yourself in and make allowances - though of course my added body weight was again an issue here. Just as well I’m not planning any Supermono comebacks, else I might have to get serious about that diet....! There was more engine braking than I was expecting from a little engine, though I suppose a Manx Norton vintage racer is only slightly bigger in capacity yet stops just as well on the overrun. I didn’t get the rear wheel chattering when braking hard from high speed for the Mallory hairpin - a problem Mark George says he regularly encounters, and which Pearce is working on a slipper clutch to resolve. Obviously not trying hard enough, was I...?!

I did learn to take advantage of the engine braking, though, coming down through the ‘box from top to second while braking for the hairpin, then notching bottom just as I laid the bike into the apex, ready to power out again while short-shifting to second for the chicane which came next. Trying to hold second meant I dropped below the 6000 rpm power threshold, and the motor would bog down when I got back on the throttle. Fun, though, once you learn how to get the best out of the little bike - and very satisfying!

And that’s the secret of what I’m confident will be the new chapter in Supermono racing which the Tigcraft R0.5 has opened. Contrary to what you might imagine, this is a bike which suits almost any rider, not only those small in stature but big in ‘cojones’, who can keep a Minimono wound on round turns where others of the point-& squirt persuasion would close their eyes and pray.

It’s a bike which rewards clean, skilled, tidy riding - but one which is also affordable &, with the huge array of potential donor motors, is surely the blueprint for the future expansion of the single-cylinder class. The 1991 Gallina Suzuki it spent the 2002 season locked in battle with for Supermono supremacy is the exact opposite of everything the Minimono stands for, and represents a decade-old traditional Supermono design path. The Minimono is the blueprint for the future - less weight, less power, less bulk, less cost - but more fun! 

Alan Cathcart