The Sportster was fitted with new cylinder head castings and port shapes in 1969. That was also the last year for a magneto ignition on the XLCH. 1971 saw the introduction of the single-spring wet clutch, and in 1972, the 883cc (55 cubic-inch) engine was replaced with the 1000cc or 61 cubic-inch engine by increasing bore size 3/16-inch to 3-3/16 inches. The new engine had 9:1 compression and was rated at 61 horsepower, which allowed the CH to rip off low 13-second quarter mile times at around 98 mph.
About that same time-actually a few years earlier, in 1970-the AMA modified the rules for Class C racing to allow for 750cc overhead-valve engines. That led the Factory into developing the new Sportster-based XR-750. The OHV XR-750 would replace the venerable side-valve KR 750 racer. The XR-750 is a de-stroked Sportster engine with twin carbs and all-new internal components. The 1970-71 models shipped with iron heads and cylinders, but was only a stopgap measure. In 1972, a new, more powerful, more reliable aluminum alloy XR-750 debuted and became the dominant dirt track racer through the next three decades.
Buddy Stubbs pieced together...
Buddy Stubbs pieced together this 45ci K model and included a KR Fairbanks-Morse magneto and straight pipes. - Buddy Stubbs Motorcycle Museum
Standard on this 1960 XLCH...
Standard on this 1960 XLCH and many other CH models was a stamped steel primary cover and horseshoe-style 3-quart oil tank. Rear brake pedal is seen on the bike's left side while the square voltage regulator sits atop the six-volt generator. - Buddy Stubbs Motorcycle Museum
This 1967 XLH Sportster includes...
This 1967 XLH Sportster includes the popular 2.25-gallon "peanut" fuel tank and oval "Ham-can" air cleaner mounted on a Tillotson diaphragm carburetor, which was used between 1966 and '71. - Buddy Stubbs Motorcycle Museum
The early to mid '70s saw an influx of fast European and Asian imports that were equaling or even surpassing the Sportster's performance. That fact and the sale of Harley to AMF seemed to change the Sportster's market position from one of a mean streetfighting hot rod to only a middleweight bike filling a product line niche.
At least, that was until the introduction of the Evolution Sportster in 1986. The new aluminum-based Evo Sportster engine opened the doors to Factory and aftermarket performance parts that again made the Evo Sporty a formidable street-fighter and racer, especially when engine displacement was bumped into the 100-plus cubic-inch range.
For anyone interested in getting a burst of adrenaline from the latest Sporty streetfighter designed for the new millennium, checkout the XL 1200N Nightster. With a wicked combination of styling, stance, performance, and bad-boy attitude, the Nightster has a gritty, urban feel offering an exhilarating ride.