Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126801
.. -..--~-------------------------------------ration, and the groundwork was thus laid for what would one day become the FZ750's engine. The advantages of the bi-convex lens-shaped combustion chamber and five-valve heads with cylinders slanted forward 45° are centralized weight mass and Jower center of gravity; full, eHective utilization of intake and exhaust pulses; straight, low-resistance intake paths with downdraughtcarburetion and straighter exhaust paths (these ideas are very popular in designing modern racing car engines, such as Formula One engines); proven durability of the inline-four design for both street and track use (it is easier to service and simpler than V-fours). The engine's capacity and drivetrain met FIM and AMA regulations: 749cc with a 68 x 51.6mm bore and stroke (these figures were best for achieving high power at high rpm), a six-speed transmission and chain final drive. In its first dyno run shortly after assembly and 'with no break-in, the 011 racing engine put out more than 128 bhp. The engineers were amazed at the engine's potential, but what was really startling was its exceptionally wide and flat torque delivery. Preliminary studies by advanced research indicated the five-valve configuration oHered torque and power gains of 8% to 10% over four-valve designs. But with a larger 750cc displacement and a new combustion chamber, torque was up 20% to 30% over four-valve counterparts. Complete fuel burning, thanks to the ideal combustion chamber shape and five-valve design, resulted in quicker combustion and higher mean effective pressure than any conventional four-stroke engine could achieve. Unfortunately, due to the worldwide slump in motorcycle sales, the oII racer and its street version repLica had to be postponed. Early in 1983, development shifted from the 01 I to another group which was to design a mass production bike, a supersports road bike, code name "OOM." The engineering goal was simple: a perfect balance of performance, handling and braking. This goal translated into "the best-performing mass production (75Occ) machine with sufficient potential for racing." Since the displacement limits had recently been changed to 750cc for TT-l racing, it was decided to add a pure supersport machine with chain final drive to the Yamaha line based on the OOM and meeting the conditions for TT-l racing. Because the OOM project was extremely important for Yamaha at the time and would influence future Yamaha four-stroke motorcycles, more strict conditions were imposed on the development group. First, the engine must remain technically advanced even after 10 years in the market; it must utilize technology already developed and proven for performance and reliabilityon Yamaha products; and it must have a clear technical advantage over the competition. These conditions led to the tripleshaft design that makes the engine more compact, rear-mounted generator, hollow chromium molybdenum camshafts, enlarged pressureequalizing holes in the crankcases that reduce pumping loss, and many other innovative features. Development of the OOM continued, wi th the 0 II as its base, toward achieving both reliability fOf every- day use on public roags and high potential for racing hop-up. High u.s. Women's MIX Championship .1 st Overall 250CC Pro: Mercedes Gonzales, Kawasaki 10th Annual 4-Stroke Nationals 1st Overall Mini 4-Stroke Dave Miller, DMC Special Florida Winter MIX Mini-Qlympics 1st Overall 125/25Occ EXpert: Bader Manneh, Kawasaki 1st Overall 65cc Stock & Mod.: Brian Swink, Kawasaki .. MAXIMA RACING LUBRICANTS 1444 Pioneer #7, EI Cajon, CA 92020 619/442-9723 CONGRATULATIONS To The WINNERS Of The 1984 Double Cross Gran Prix Team Championships The cream of the 1984 racing season met It Perris Raceway on Sunday, December 9th to decide who were the best G.P. riders. Split into five teams of equal combinations of Beginners. Novices, Amateurs and Expens. and three Mini teams in a separate event. they went head to head for an hour and. half with the Blue Team capturing the title and the $3000 in prizes from Southland Suzuki. Malcolm Smith Products. Sunwest Cycles. Tustin Honda. Ceet Racing Products and Team Tamm. 1984 GRAN PRIX CHAMPIONS - MINI DIVISION: RED TEAM ... . ~ Eric Haug. Larry Pacheco. Joe Hebdon. Willis Drake. Cory Reeves. Don Clark. Stan Hase and Teddy Williams. A Product of 18700 N0rm8ndle Ave.. "C". Glircten8, CA (2131 327-3432 !\'AII!\'I .-R~L~. 10% Off Sale Now eveilebMlln Notttt.n CaIifomi••t Schilling RACING FRAMES W. HAlf. A COMnETZ LlIf. OF DIRT TRACK CHM.(• • COMNIf.IfTS. CARROLL RACIIIG 'Continul!d to pagl! 74) - MAXIMA RACING LUBRICANTS 1444 Pioneer #7, EI Cajon, CA 92020 619 / 442-9723 BELLFLOWER YAMAHA Prod_. ~.O ...... 7al, Yubo Chv. CA lall,. F.. .................. _ _._1I'11173·3_. ~_" ~ All Parts and Accessories Ad mus! bfI preNflled 10, discount 10401 AJonch ~.CA (m)~5017 71