Yamaha TZ350
The incredible TZ350, a brief history
1973 saw the introduction of the bike which was about to transform the 350cc GP class worldwide, the incredible TZ350A. The inclusion of water-cooling in addition to other slight improvements over the bike's air cooled predecessors, the TR2, TR2B and TR3, saw Yamaha's 350cc production offering fast becoming an almost unbeatable weapon in the hands of the right rider. Internally the motor hadn't changed much from the previous model apart from the widths and angles of the transfers being altered to improve scavenging, though actual port timing remained as it was with the older model. Also the silicon content of the cylinder was lower compared to that of the TR3's separate hypereutectic units. The new bike produced a very respectable 60bhp @9,500rpm.
Interestingly, there was no variable advance built into the Hitachi TIA02-01 CDI controller used on the 350. Whatever ignition advance the tuner set was the advance right through the rev range. ( This was not the case with the TZ 250 ).