- Your note: hello biker people.. I have just got my hands on an old 350 yamaha. now the serial number on the motor starts with R5-______. - now,that,i believe means the motor was made in 1970. The gas tank color is tangerine and white , which i think is the colors for 1971. So am i correct in assuming that the motor was built in 1970 but out on a frame and sold as a 1971? and am i correct in that the motors were excectly the same in 70,71,and 72? thanks charlie. REPLY: Charlie - I have two (2) Yamaha R5 350cc two stroke twins; (1) is VIN: R5-00331 (1970) and (1) is VIN: R5-121195 (1972). Engine and frame for both have the same VIN. - Internals are the same but there are some minor differences in external cases. I have riden the 1970 for the past 10+ years. Since it is piston port and the later RD350 is reed valve induction the pistons are different and not made by aftermaket (ie. Weisco), so all that is available is NOS Yamaha; and, they are expensive! Top end can be converted to RD (Cyls, Pistons, Reed Vlv., Carbs, Heads); but, you will still only have a 5 speed gear box. This is why most people prefer the RD. I am presently in the process of putting an RD250 engine into my 1970 R5 and working on two other engines I have (an RD350 and an RD400). I will keep the R5 engine in case I find reasonably prices pistons somewhere; but, for now, I´m looking for something to ride. ... Dick J - NY