Roberto Pietri's 1997 Yoshimura GS1000

Below you find an article from the "Classic Racer" magazine with some info about Roberto Pietri's '97 "Honda test mule" for which he alledgedly paid 10.000USD at the time. And fantastic detail pictures made by current owner and AMA superbike maniac Brian O' Shea...

The early days of Superbike racing, dating back to the birth of the class in California, now seem shrouded in mystery and intrigue. In the two decades plus since the birth of four-stroke street bike racing, names including Yoshimura, Muzzy, Pridmore and McLaughlin have acquired legendary status. Anyone with an ear for a good folk story can tell you why.

This combination of wary NASCAR 'run what you brung' charm, alleged backyard mechanical creativity and hairy-chested riding skills yielded some amazing action, both on and off the track. superbike competition remains a branch of bike sport that many contend is the most exciting class on view today..... period. And it all started in the US in the mid 70s.

When Classic Racer first asked for an article looking back on the early days of the Superbike Championship, first it considered an accurate, historically fair overview. No gossip or unsubstantiated rumour allowed. However that type of coverage just doesn't do justice to the 1025cc era of the AMA Superbike National Championship. Although we didn't know all the players and can't confirm every story, there is no doubt that the Superbike scene was a wild and woolly arena when Honda decided to jump in. Spanning the era from the birth of the modified production national class in 1976, to the switch to 750cc class limit in 1983, these truly were the outlaw days of Superbike competition. With motors huge in both displacement and physical size, puny frames, narrow tyres and dirt-track handle-bars, the Superbikes of this period seem almost cartoonish compared to todays sleek replica-racers.

Even so, these bikes have inspired an avenue of street development that's still evident today in many of the latest Japanese retro sporters. 'Naked bike' racing is nothing if not a tribute to the riding styles developed by the likes of Steve mcLaughlin, Reg Pridmore, Wes Cooley, Eddie lawson, Freddie Spencer and Wayne Rainey, to name a few.
Offical AMA Superbike racing started in 1977 with works BMW domination, but most competitors viewed the class as a stomping ground for Kawasaki's fearsome Z1. Next, Suzuki arrived with its four-valve-cylinder GS model line, further defining the category. when Honda stepped up with it's full-on factory programme in 1980, the days of upset wins for the small European builders, including Ducati, Moto Guzzi and BMW, were over.

Prior To Honda's arrival in March of 1980 at Daytona, factory efforts in AMA Superbike competition had a low key, budget-oriented appearance. Honda made it clear that Superbike racing was a no nonsense activity, and forced the other teams to take note. Ironically, Yoshimura's unfinished hot-rod approach and Kawasaki's we have complete faith in Rob Muzzy's tactics were the perfect foils for the Honda racing machine..Try as it might, American Honda couldn't win the Superbike crown until the other Japanese manufacturers briefly backed out of the class. By that time Kawasaki's primitive air-cooled in-line four had stopped the high-tech Honda assault one more time, in 1983. That was the first year of the 750cc displacement limit for Superbikes, a class change seemingly tailor-made for Honda. Even so, Honda built some great bikes and fielded top guns in the early years of it's Superbike efforts in the US.

During the autumn of 1979, the roadracing community in the US was busy discussing Honda's impending arrival in the class. While most outfits tidied up their existing machines, Honda was working flat out on a top secret development effort, utilising several different motorcycles.

Wes Cooley earned the 79 title for Yoshimura Suzuki's GS1000, even though the popular shaggy Californian didn't manage to win any of the races. Filling in for the injured Mike Baldwin at Kawasaki, Feddie Spencer took two victories, and headed Honda's shopping list.

McLaughlin was signed to lead Honda's effort, both on and on the track. Top privateer racer McLaughlin was the man who established the AMA rules for the class and went on to set-up the World Superbike series. McLaughlin was a front-runner on two-stroke Yamaha equipment throughout the 70s, but his name became synonymous with the cult of street-based superbikers. Fresh from a season on Racecrafters Kawasaki's, McLaughlin had an intimate knowledge of the series and its rule subtleties. Prior to his unproductive stint with brilliant builder Des Roches at Racecrafters, McLaughlin had piloted one of the dominant factory Butler and Smith BMW's as well as winning with the first-ever development Yoshimura-Susuki GS.

Honda principal McLaughlin, slated to race as well as manage,was charged with a serous task, the return of Honda to US competition. While the official premier AMA series was for F1 machines, and dominated to the point of boredom by Yamaha's TZ750, the Superbike series was going through a boom period.

Honda's return was geared to fit in with the rise in street bike-based competition, since in this era Honda was considered a 'four-stoke only' company. Some industry insiders were playing up Honda's growing success in the car market as a lack of commitment to motorcycles, and a major US Superbike programme seemed the perfect solution to several image and marketing problems.
With the launch of the all-new DOHC four- valve-per-cylinder CB750F in 1979, Honda finally had a suitable model to form the basis for a modern superbike. Techically, Honda's 'F model' was in line with Suzuki's four-valve TSCC design, and was a supposed step ahead from the two-valve-per cylinder Z1.

The first, ground-breaking in-line, four-cylinder Superbike, Honda's prototypical two-valve-per-cylinder CB750, was lauched in 1969. Although cosmetically refined, the CB750 was well past it's prime as a sportster when the giant US branch of Honda received it's much requested replacement.

One of McLaughlin's many friends was international playboy and racer Roberto Pietri, a sometimes 500cc GP racer aboard a Suzuki RG500, and a top US privateer. Officially based in in Venezuela, with considerable family money, 24-year-old Pietri lived in Hollywood. During 1979 he ran a Yamaha TZ750 as well as a full works Yoshimura Suzuki for his 'Hole In the Wall Gang' team in the US.

Excited by the promise of a works Honda in 1980, Peitri presented McLaughlin's just formed Honda squad with his GS for evaluation. Needless to say, this deal didn't sit well with Yoshimura, who didn't forgive Pietri for taking the bike he'd paid for to the competition--- especially since the machine eventually ended up in Honda's raceshop back in Japan!

By October 79, Mclaughlin and his small crew were conducting dyno, road course and drag strip sessions at several Californian venues, including Willow Springs and the now defunct Riverside. The stealth Honda crew compared the Pietri Suzuki to a development 'mule' 1000cc CB750F, as well as the lightly-tuned racer used on the east coast during 1979 by veteran Kurt Liebmann. A long time Honda stalwart. Liebmann was one of the first riders to get the racing version of the previous Honda four, the CR750, in the early 70's.

Soon a rare Honda F1 machine would jion the test fleet, direct from the UK. With a custom racing frame, sand-cast cases, big CV carbs and a claimed dry weight of 364 lbs, the ex-Alex George endurance bike would help establish a goal in terms of performance. George was even jetted in from the UK to help with the track test programme. During a particular test session, one of the team's tuners, Mike Velasco, was out on the track, breaking-in a motor in one of the street=based machines, while Mclaughlin tried the F1 racer. At the time , Velasco was a top club racer, and supplied parts from his own Superbike for appraisal by Honda. Velasco and McLaughlin eventually started racing, much to the delight of the crew membersand the dismay of the Japanese technicians on hand!

To set a bench-mark for the programme, Mclaughlin made sure that they got the most out of Pietri's Suzuki, eventually recording an out-puy of 125 bhp, measured at the crank. As well, the Yoshimura machince went through the traps at the end of the Orange County quarter-mile drag-stripat an impresive31 mph, in roadrace trim.

The first CB750F-based engines, provided by RSC (Racing Service Centre, precursor to HRC) in Japan, produced 104 bhp. RSC claimed a 140 bhp yield, about equal to what the final versions of the engines would generate in late 1982! Using the Japanese power-plant as a base, the Americans were soon up to 116 bhp at 9000 rpm. The small team divided their dyno time between their official home at Honda's head office, and the more usable environment of Jerry Branch's famed facility. soon Branch would be developing radical heads for the 1025cc Honda, addressing one area of the DOHC design that proved to be less than ideal.

Shortly before Chrismas 1979, Mclaughlin and some of the crew made a quick trip to Japan, to establish requirements for the official machines. While the 'final' configuration was established at Honda R&D, the rest of the squad was pursuing the hot-rod approach back at the under construction race shop in Gardena California.

When McLaughlin returned to the US, former BMW US race boss, Udo Gietl, jioned the team, to serve as a more 'hands on' team manager. This would allow McLaughlin to start concentrating on his riding. But just as the factory BMW twins were not quite identical to the street bikes they were based on, Mclaughlin and Gietl had big plans for the soon to arrive, first ever batch of four factory Honda Superbikes.

The four pristine, stock-appearing Honda's arrived in the US at the end of January, ready to race right out of the box. The engines were run-in in Japan, but a quick examination showed that rod bearing and cam chain tensioner problems were already developing, following a pattern recognised during US development. While some of the team of six tuners/fabricators set about updating the Japanese engines, major surgery was also scheduled for the chassis.

Joining the team at this point was famed east coast builder Todd Schuster, a giant of a man who could fabricate just about anything, and had done exactly that with the infamous factory R90S model BMW's. Mclaughlin had some very specific requirements in terms of frame geometry, and soon all four bikes were cut completely apart in the quest for a better set-up. the race shop was barely completed, and now the whole crew would work continuous 20-hour days, seven days a week, in preperation for their offical debut.

With limited time, if not resources, and Daytona's early March start approaching fast, the frames were reworked by Schuster using just plan gas welding instead of the preferred Tig. The team members were after a perfect 50/50 fron/rear weight bias, not the 45/55 stock arrangement. The steering head was moved back an inch, and the upper shock mount area was braced.

At the time, the AMA rules were somewhat fluid, and the team's changes fell into line with if slightly ahead of what Yoshimura was up too. Since Yoshimura set the standard in terms of 'rules interpretation', these revisionswere crucial, less the team 'fall behind in it's cheating'- as the NASCAR boys like to say. When completed the frames had McLaughlin's goal of perfect 50/50 weight placement. As one insider put it at the time, 'the AMA love to look at motors, but they don't pay much attention to frames'. That would turn out to be a major issue at the end of 1980 Initially, most of the running gear, including the trick stock looking triple clamps, was used as delivered from Japan. Forks were reworked Goldwing units, while the rear shocks were developed as a special project by Mulholland-Interpart in the US. Mulholland was one of the first shock builders with a serious dyno testing facility, and everyone had been most impressed with the test performance of the works Japanese KYB units taken from Pietri's Suzuki. At the time Yoshimura didn't get a lot of factory support from Suzuki US, but its direct Japanese pipeline provided 500cc GP quality running gear. Un fortunately, some of the 'back door' RG works parts needed serious beefinf up for use on the much heavier superbikes. Unable to duplicate the adjustability found in the KYB's Mulholland built a series of shocks to duplicate a wide range of control options. At the time, most racers didn't know what damping was, and vitually no Superbike had much left by the end of a race! In the late 1970's, even the top riders routinely used the same Goodyear slick throughout an entire race weekend, so today's detailed traction concerns simply didn't apply.

Back at the dyno, the team leaned that careful beak-in for the wet sump engines was crucial to durability. Otherwise rod bearings would soon fail due to stavation, and re-routeing of the oil inside the motor only partially solved the problem. Eventually a seperate oil pump and oil tank with positive feed fixed the problem. Seeking the kind of horse power that would be required to rival the heavily developed Pops Yoshimura fettled Suzuki's, Honda ran into considerable trouble with the radically angled valves in theF model's head. Aflatter valve position( a la Suzuki) would have been better, and the closely bunched valves didn't flow nearly as well as had been hoped. Cam chain tensioners caused trouble, but in the end a whole new system, with a solid plastic/nylon runner fixed the problem. That development was still months away. Also in the works was a new type of cam, designed by Gietl and eventually produced by Crane Cams in 1981.

Another brand new product, Ei model 'blue plastic' carbs, showed impressive peak output numbers on the dyno. Unfortunately, no linkage was avaliable for the set-up, so four seperate cables were required to operate the system. With the appropriate return spring few riders could hold the very stiff throttle open, and softer springs led to sticking problems. Even so most of Honda's four riders used the ever-improving not yet available Ei carbswhen possible. When a linkage arrangment was perfected, the carbs became more popular with all the teams, now badged as Quicksilver racing carbs.

Just prior to Daytona, the hybrid engines, using mostly Japanese parts but some US bits, were making 122 bhp at the crank with 11.9: 1 compression ratio. At the time, the team was using a Bassani pipe and denco cams, both favoured by Mclaughlin after his works with Kawasaki. Blue H&H race fuel produced the best power output, so H7H became Honda's gas supplier.

When Honda's crew of Japanese engineers and technicians arrived in California for the pre-Daytona team meetings, they were shocked to see that 'their' bikes were no longer in existence. While no one can say what American Honda spent on the projectthe first year, guesses of more than one million US dollars were commonplace. As one technician who subcontracted on the effort explained: "No-one ever said stop when it came to parts for development"