the "combat" engine was released in january 1972 with a twin roller bearing crank, 10:1 compression and developing at 6,500 rpm. reliability immediately suffered, with frequent and early crank-shaft main-bearing failures, sometimes leading to broken crankshafts. older engines had used one ball-bearing main bearing and one roller bearing main bearing but the combat engine featured two roller bearings in a mistaken belief this would strengthen the bottom-end to cope with the higher power-output. instead the resultant crank-bending caused the rollers to "dig-in" to the races, causing rapid failure. this fragility was particularly obvious when measured against the reliability of contemporary japanese machines. this problem was solved initially by a special roller bearing of 'superblend' fame later in 1972. this was superseded by a standard high capacity roller bearing early in 1973.