Champion Yamaha

Technical Details

Year Built : 1971 Engine : 750 cc OHC Transmission : 5 Speed Electrics : Hitachi CDI magneto with internal rotor Notable Features : As the 1970's rolled along motorcycle racing was going strong, Displayed here is what resulted from the desire to own & race a 750cc Harley-Davidson and the " slight problem " involved : A new XR-750 was out-of-reach. The logical alternative was to build the next best thing that could make dependable power and that meant modifying a Yamaha XS1 motor. During Spring 1974 a low-mileage 1971 Yamaha XS1-B ( VIN S650-017061 ) was purchased in Houston, Texas. The cycle was identical to its XS1 " brother " as shown on Page 2 which oddly enough came down Yamaha's production line forty bikes apart ( VIN S650-017020 ). Readily available engine mods included parts from Shell Thuett / Shell Racing Specialties : 750cc BRC slipper-pistons & cylinder sleeves, Number 1 cam, S&W valve springs & collars, Alloy intake manifolds with 34 mm Mikuni VM carbs, and TT headers. Machine work was performed to install the big-bore sleeves and deck the cylinder. Head work was the usual porting & matching the new intake manifolds, setting-up the valve springs, contouring the intake valves along with precision work to equalize the valve seat widths. Crankshaft was rebuilt completely with all new connecting-rods, crank pins, and bearings. Motorcycle dynos during those days were only comparative devices but a similarly modified motor was tested and the calculated rear-wheel horsepower ranged into the upper 60's or aprox 1.5 HP per cubic inch. To house the hot-rodded motor a new nickel-plated Champion frame kit was purchased from Gerry Booher at USC, Up front is a Kennedy spool hub wheel with WM-2 Akront, Rear wheel with WM-3 Akront and quick-change sprockets was supplied by R/W Racing Wheels out of Oklahoma City, S&W rear shocks & springs, 35 mm Ceriani MX forks were used initially but later changed to Ceriani road racers purchased from Neil Keen, Fuel tank & seat combo was modified and painted in traditional Yamaha team colors by Danny Ericksons in Carlsbad, Calif. After completion & testing the bike was raced at local Houston tracks in amateur open-class events. Naturally a few changes were made : At first ignition was supplied by battery & coil that proved troublesome, An early Honda " Red Wire " coil was considered but ultimately a Yamaha CDI system was adapted that proved fast, reliable, & always ready to fire. After the first few races the MX fork felt soft and was upgraded to the RR type. Soon after Goodyear came out with their first DT II series tires and the wider front tire necessitated reinstalling the MX fork crowns. That proved to be the best combo for rake & trail. At the same time the rear rim was changed to a WM-4 size in order to accommodate the rear's new profile. For various reasons the bike was never raced again. But it was used for practice and to gain experience. It's difficult to guess how many miles have been ridden but the number is " up there ". Many of those joy rides have been flat out in high gear wherever long stretches were available. The most common areas were where Highway 288 was being built from Houston to Freeport and East Beach on Galveston Island. When built right & maintained the Yamaha XS1 motors are nearly bullet-proof. This rig remains in immaculate condition and has never been crashed or abused. Unlike most Champion frames the rear frame loop is still in factory-new condition. No repairs have been needed and the frame still has its original nickel plating. The serial number reads as clear as the day it was stamped by Doug Schwerma & Co : Yam 4 - 1035. After relocating to Fort Worth there were times when races at the Devil's Bowl were " calling " but the Yamaha always stayed home. All's well that stays well. Amen.

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