Originally Posted by Sadler

The 7500/7500 Plus is a twin-piped 340cc L/C the rest of the family is the 5500/5500MX's running a F/C Type 503 with 496cc's, the 6500 was replaced by the 7500 (I think in '78-'79) and used either the F/C 496cc or the 340cc L/C depending on which year or if it was a Plus model or not, and the big daddy 9500/9500Plus using one of three motors(I think) late 70's to earlier 80's are a 440cc L/C twin with twin pipes, the same L/C twin Type 462 4??cc from the SS25 and I think the last year('84) saw the big type 534/537's 521cc L/C twin found in later Formulas.