Suzuki XR69 – Classic Motobikes – Bike Reviews

24 Apr 2015 | Author: | Comments Off on Suzuki XR69 – Classic Motobikes – Bike Reviews
Suzuki B-King Final Prototype

Suzuki XR69

With the late 70s came the resurgence of big capacity four-stroke racing after a mixed few years. F750 began earlier in that decade as road machines grew in size and gave a platform for the Triumph and BSA triples to compete against the Nortons, Harleys and Ducatis on the racetracks of the world. Before too long the Japanese invaded with their screaming, some times roadster based, two strokes, and devastated any hopes of the roadster based four-stroke ever competing fairly and squarely.

The answer was simple, effectively outlaw the two strokes and introduce a class for 1000cc machines based upon road engines as the original Formula dictated.

The origins of the XR69 date back to 1976 when Pops Yoshimura approached Suzuki for help with his GS750 based racer. This arrangement suited Suzuki perfectly as they possessed little knowledge of high performance four-stroke engines, while Yoshimura’s development work freed up the resources of the already stretched Grand Prix race department, and gave them competitive four-stroke race machines in the process. The bond between Suzuki and the iconic tuning shop still stands today with strong links between Yoshimura and every aspect of Suzuki’s race and road bike efforts.

By 1978 the work had begun on a 1000cc race machine based heavily upon the GS1000 roadster, but Yoshimura soon found that the power they had unleashed, around 130bhp, was surpassing the road frames capabilities by a huge amount, Suzuki responded by allowing chassis parts and design concepts from the 500cc GP race machinery to be used, and the transformation was stunning.

A steel tube frame, similar in appearance to the XR23 racer, was wrapped around the four-cylinder air-cooled engine, while the bouncy bits were handled by GP spec Kayaba rear suspension and forks. Graeme Crosby joined Suzuki for the 1980 season following a successful year as a privateer, one of his first jobs was to test the new GS1000 derived racer, he was suitably impressed claiming it to be one of his all time favourite race bikes. His development work was put to great effect and within weeks took the machines first win at Daytona before going on to be a dominant force in all major race meetings during that year.

The complete package was ready for the start of the 1980 season and ahead lay the huge task of beating the dominant Honda RS machines at their own game. The Suzuki proved to be more than up to the job however and from the outset, despite its relatively low budget development, especially when compared to the effort Honda made getting their CB900F based racers up to speed, the XR was at the head of any field Suzuki chose to put it in.

The technology behind the Suzuki was also a little dated, using only two valves per cylinder, while modern thinking saw at least four valves as the required amount. Pops Yoshimura had already amassed years of thinking with this design and opened up the ports, the original 38mm inlet vales grew by 1mm while the exhaust went up from 32mm to a whopping 37. This saw the power rise in excess of 130bhp but shortened the life of the Suzuki piston to a mere, two-stroke like, 500miles.

The answer was found in the UK and special forged Omega pistons where fitted solving the longevity problems completely.

One notable trait when riding the XR is a high tick over, the extreme valve timing implemented by Yoshimura in order to get the high power outputs means low speed running is poor indeed, this is rectified by keeping the revs up above 3500rpm at all times. It is a little hard to get used to at first, as the feeling is like the throttle is stuck, but once factored in to last minute down shifts, the end result is no different. That characteristic apart and the XR is a stunning machine, sweet handling thanks to its high pedigree donors and fast too with a top speed in excess of 170mph depending upon final gearing.

A year after the XR69s launch, the rear end came in for revision once again in keeping with the two stroke GP racers of the time, the twin Kayaba suspension units being replaced by the all new Full Floater suspension that would later see action in one form or another on most Suzuki road machines.

The XR69 was the bike to have for Superbike racing in the early 80s, both short circuit and road racing showed the big Suzook to be ultra competitive, much to Honda UK’s chagrin. Honda had come to view the TT races as theirs by right, but the much smaller, and smaller budget, Suzuki team had different ideas rising to complete dominance by the end of the XR’s reign in 1984.

Suzuki B-King Final Prototype

During 1982 Roger Marshall and the factory XR69 proved so successful in the British championships that he earned the nickname “A win a week” Marshall. The Lincolnshire rider won every championship he entered that year, and became hot property in the process, Honda tempting him away for the trusty XR69 with a substantial money offer to ride for them in the 83 season.

This left Mick Grant as the sole experienced rider in the Suzuki camp with relative newcomer Rob McElnea joining him taking Marshall’s XR69 ride in the process. McElnea dominated the TT that year on his XR69 with some impressive rides on the semi factory RG500 thrown if for good measure. Some modifications were implemented on the XR69 for this season, the most important of these being the dry clutch conversion, making it easier on the rider’s left hand, and liberating a few more horses in the process.

By the end of 1983 the time of the XR69 was over. Rule changes within the Superbike and TTf1 class meant an overall reduction in capacity to 750cc for four strokes and 500cc for two strokes. Strangely, as the earlier rule change in the late 70s was to favour the new breed of four stroke machines, this allowed a run of success again for roadster based strokers with the Suzuki RG500 taking the UK F1 title in 1986.

The rules once again changed in 2004 allowing 1000cc machines to compete in the Superbike class.

Suzuki XR69 Timeline

The first prototype Yoshimura engines were developed but needed a better chassis than the road machine could provide

Graeme Crosby tests the new XR69 and goes on to win the Daytona 200 with one. He also wins the TT Formula One World Championship as well as finishing 2nd in the British TT F1. He also won the Australian Swann series and the Suzuka 8hrs sharing a full factory specification XR69 with US rider Wes Cooley.

Suzuki B-King Final Prototype
Suzuki B-King Final Prototype
Suzuki B-King Final Prototype
Suzuki B-King Final Prototype
Suzuki B-King Final Prototype
Suzuki B-King Final Prototype


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