Michael Scott | August 11, 2021
Right at the death of the two-stroke 500s came the finest one yet—built by a few Americans, Aussies and Brits in a warehouse in the UK
By Michael Scott | Photography by MS Archives, Gold & Goose
It was murder, plain and simple. Murder by committee. Two-strokes got the chop.
Among the victims were some of the most elegantly beautiful racing motorcycles ever made, and certainly the fastest of their kind.
The V3 Protons, created by a legend and crafted by engineering artists, were cut short in their prime. Not before, however, one of the lithe, lightweight triples claimed a final pole position ahead of the new MotoGP monsters at Phillip Island. Jeremy McWilliams set the fastest-ever lap of what was then the fastest track on the calendar.
That achievement was a final high point, confirming the Proton’s status as the fastest two-stroke GP bike ever. A fact confirmed by the best two-stroke laps and race times at several other circuits in a 2002 season that redrew the floorplan of motorcycle grand prix racing.
It was an interim year, with 500cc two-strokes permitted to continue against the new MotoGP four-strokes, whose 990cc maximum capacity distinguished them from lowly production-based Superbikes.
At the end of 2001, Valentino Rossi had won the final all-two-stroke 500cc championship, his first of seven titles, and he expressed the views of many when he deplored the new generation of what were dubbed “the diesels.” Four-strokes were inevitably heavier and clumsier than the feisty, highly developed 500cc two-strokes, and thus considered less pure-bred race bikes.
Valentino tested Honda’s clever new V5 RC211V and said at first that he’d prefer to stick with the NSR500. He was persuaded to change only after back-to-back tests with a revised RCV yielded a faster lap time.
The battle through the year had been interesting but skewed. Throughout. Rossi won 11 of 16 races, and four-strokes took all of them, although Alex Barros ran him close at rhythmic Assen, a track of complicated fast corners and no real straights.
This well illustrated the problems facing the many riders—in factory B-teams or satellite squads—stuck on last year’s NSRs and Yamaha YZRs. The lighter two-strokes could easily achieve higher corner speeds but were overwhelmed in acceleration and maximum speed. The diesels would get in front off the start line, then get in the way through the twisties.
In this way, having a faster lap time didn’t help. Two-strokes were doomed, deliberately so, by rules that gave four-strokes a double-size advantage impossible to overcome.
It was the worst possible timing for the Proton. If only they’d had one more two-stroke-only year, the final iteration of Kenny Roberts’s dream of challenging the Japanese factories had every chance of success.
It had begun seven years earlier, with a typically maverick decision by Roberts, the former triple champion now a dominant team manager for Yamaha.
Kenny was still a king, but something chafed. He would describe his factory Marlboro Yamahas as “sticker bikes,” bemoaning how, at year’s end, the factory took them back. This not only undervalued the role of the team’s engineers, but also left the team with nothing beyond their trophies, their vehicles, and their wage bill.
Kenny’s move to become a racing manufacturer in his own right was typically bull-headed, but the pitfalls were not all his own making.
Backing and the name Modenas came from a Malaysian scooter manufacturer, but the technology was British, and inspired by the light and agile three-cylinder Honda on which young Freddie Spencer narrowly beat Kenny’s own more powerful V4 Yamaha in 1983. Kenny knew to his cost just how effective better braking and corner speed could be in a sustained season-long battle.
The rules were helpful, with a minimum weight of 253 pounds for a triple compared with 286 pounds for a four-cylinder.
Team Roberts engineers, led by the late Australian Warren Willing, developed and modernized the idea, but renowned race-car engineer Tom Walkinshaw, his TWR firm prominent in the English “Formula One Belt” surrounding Team Roberts’s Banbury base, was responsible for final design and manufacture of the V3 engine.
Work started during 1996, and when the bike took to the tracks in 1997, it was condemned to go through early development very much in public. This proved rather embarrassing, for there were many teething troubles and breakdowns for the riders, French ex-off-road superstar Jean-Michel Bayle and Kenny’s eldest son Kenny Junior.
Results up against the established and experienced Honda, Yamaha and Suzuki were now and then respectable: Bayle qualified on the front row at Brno and achieved three eighth places (Junior got two).
The Mk1 Modenas had an over-riding flaw, explains Team Roberts stalwart Tom O’Kane, nowadays heading Suzuki’s MotoGP test team. “It was a very clever bike, but some ideas were ahead of their time.”
One original feature of the two-down/one-up V3 engine was that two adjacent cylinders shared a common crankcase volume, with one down-cylinder piston rising and falling in sync with its adjacent up cylinder, and no main-bearing between them. “We used to call it ‘a flying web’, because the middle crank web was unsupported, with a crank-pin on each side of it [disposed at the angle of the V].
“It was an ambitious design, and there were certain issues with cylinder filling, with two carbs feeding into the same crankcase volume.”
Another unconventional feature was the under-seat radiator, fed by an air duct beneath the fuel tank.
There were more ill-advised adventures, O’Kane continued. “That first bike had standpipe carburetors, which were also custom made.” These replace the usual float-bowl/needle valve with a weir system. “With Yamaha, we’d been having float-chamber problems when we pressurized the airbox.” The special carbs were meant to obviate these difficulties.
All of these were undermined by a single basic problem—ruinous vibration. “There was a decision made early on that it wouldn’t have a balance shaft, so the vibration level was quite high. We went back to conventional carburetors and radiator position, but without a balance shaft… you can’t retro-fit one.”
I summed up the problems in that year’s Motocourse—“vibration so severe that it snapped footrest hangers, frothed the fuel and the coolant, chafed through wiring, caused component failures and in general subjected the bike and its riders to a constant destruction test.” Roberts blamed a misleading promise of greater stiffness from the crankshaft manufacturer.
Clearly, a redesign was required. It came with a surprising degree of help and cooperation from the Japanese rivals, largely (explains O’Kane) because of the friendship and respect for Kenny.
There were three key figures—the chief of Keihin Carburetors Mr. Ito, HRC director Yoichi Oguma, and Yamaha’s “Mike” Maekawa.
The Mk2 machine didn’t appear until the latter half of 1998, and reversed the layout, with two cylinders up and one down. It also had a balance-shaft and was essentially designed and built in Japan.
O’Kane explains: “The parts were made by specialized engineering companies with experience supplying the existing teams. So, there was quite a crossover, and they were companies we would never have access to without Kenny being Kenny.”
This help for rivals, continued O’Kane, was not unusual, “for, let’s say, small operations. We’d supported the Patons back in the Yamaha days; Yamaha were likewise very generous with their resources and their advice when Cagiva were being developed.
“The paddock is a family, and nobody wants to see anybody being humiliated. It’s a very Japanese thing.”
The second engine eliminated the vibration with a balance shaft. But this brought its own problems. “It was basically quite long. The layout of the shafts was like an older design, less ‘stacked’ than current designs. That meant we couldn’t get the chassis performance we wanted.”
And how: 1999 was the worst season yet. Junior and Warren Willing had both gone to Suzuki, Bayle was hurt and retired mid-year; several riders including David de Gea, James Whitham and Mike Hale faced all sorts of problems.
But Mk2 bought the team time to design and build the ultimate KR3.
British engineer John McGee was a crucial addition. He designed a compact and well-balanced bike, which rider McWilliams describes as “the most beautiful bike I ever rode… the bike I felt more at home on than anything else.
“The thing was like a little toy—so easy to flick, to steer. You could put it wherever you wanted, and it delivered the power so smoothly and seemed to get a lot of grip from the tire. By the end of 2002 we were pretty much on equal footing with the V4s. Lacked a little bit of top speed, but you’d make it up on the brakes and in the corners.”
At the same time, “it was such a clean, efficient little motor, you could literally put lights on it and ride it to the shops—it would tick over at the lights.
“I think dropping two-strokes was a mistake. A 500cc two-stroke went 202 mph way back in 1993. Had we continued with development, with the current injection technology, I reckon two-strokes would be going quite a bit faster than the current four-strokes, and they would be incredible to watch.”
KTM’s development of off-road two-strokes, in which McWilliams played a role, proved them cleaner than four-strokes as well. “And nothing beats the sound a two-stroke,” he added.
Sadly, in GP racing, they culminated with the KR3, the fastest two-stroke racing bike ever built. And a tribute to the only British team to make a serious GP bike since Norton and Matchless in the distant past. CN
VIDEO | Proton KR3 Kenny Roberts Runs after 15 years
The Banbury Sweat-Shop
What was life like in the sometimes 24-hour Banbury sweat-shop where Kenny Roberts built his grand prix bikes?
For O’Kane, “they were the best years of my career.”
At Kenny’s insistence, everything was custom made. “For example, choosing a power-valve motor. You could go to your local Yamaha racing spares shop and buy the ones for the YZR 250. Trouble is they would look identical to the Yamaha’s, and it would look–at the very least–like we’d copied them. So, I ended up designing them from scratch. We had a carbon housing, some Swiss DC motors, and everything was custom made.
“The electrical generators, most of the parts for them came from a company in England making disc brakes for mountain bikes. I went to them because none of the engineering companies in the Midlands had time for small, fiddly items. They were all too busy doing F1 stuff or bigger projects. So our generator rotor was put together using bicycle crank tools, funnily enough, the spanners for bicycles.
“That was one of my jobs for the two-stroke period.
“At that time, we were having debates on which way to spin the crankshaft, so we had primary chains and sprockets made [in addition to the established gear primary drive]. In one practice session, with Mike Hale riding, we did one run with sprockets, then clutch off, cover off, sprockets off and primary gears on, and on the other side the trigger wheel for the ignition. Then the bike went out with the crank running in the opposite direction. We did that in one practice session. Really good information… same bike, same rider, same tires, same session.
The other factories were also experimenting like that, but I doubt very much ever on the same bike in the same session.”
The Two-Strokes’ Last (Muted) Hurrah
On a windy weekend in late October, the Australian GP was the second-last race of the 2002 season, and the last real chance for two-strokes to challenge the new MotoGP order.
Phillip Island is fast and rhythmic, and most importantly had only two slow corners, neither leading onto straights, so the acceleration advantage of the big bikes was offset by the better braking and higher corners speed of the 500s.
McWilliams’s sleek little silver triple was slowest down the straight, at 186.6 mph. Rossi’s Honda was fastest at 201.01.
Yet the Proton was on pole, a first for the little gem. The achievement was underlined by his companions on what was then a four-strong front row, uniquely all two-stroke: Garry McCoy’s Yamaha YZR, Nobu Aoki’s second Proton and Jurgen van den Goorbergh’s Honda NSR.
There was a trick to it. For the first time in memory, there was not a single Michelin tire. The Protons and the Honda were on Bridgestones, McCoy on Dunlops. And Michelin had not brought super-soft qualifying tires. As Alex Barros, leading row two, said: “The front row is a mirage… they all used chewing-gum tires.”
Sunday proved him right. Those 990s are great big bullies, but recollections of the race will always be enhanced with the memory of Aoki in particular harrying Max Biaggi’s Yamaha throughout. Though he led over the line four times in 27 laps, he was overtaken every time by Turn One, making it imperative to get ahead as soon as possible thereafter, with some highly daring riding and quite extraordinary angles of lean. “I must have been like a fly to Max, but it was what I had to do,” he explained happily afterwards, while team boss Roberts came out with the quote of the weekend. “It’s like when your dog gets real old and sick, and you have to take her to the vet to be put down. And in the car, she gets all frisky. That’s what our bike’s doing.”
The win was contested between Rossi and Barros, decided when the latter ran straight at the hairpin. Valentino’s 50th career win.
McWilliams had a frustrating afternoon. Slow off the line, he was 14th on lap one and charging through when trouble from his still-cool carbon brakes saw him run off at Honda hairpin. He rejoined last and set furious lap times close to those of the leaders as he pulled through to 10th.
Van den Goorbergh finished top two-stroke, fifth on the NSR; Aoki was seventh. And Aoki was top two-stroke in the championship—12th, with McWilliams 14th.
The Protons appeared a handful of times in 2003 as Team Roberts scrabbled to catch up with their own four-stroke project, but their time was over.