Yamaha released it's first production 125cc
roadracer, the TA 125, in early 1974 and advertised
it as a "Clubman level Production Racer".
The TA 125 was a twin cylinder, air cooled,
two stroke, twin shocked racer based on the
company's successful AS-3 roadbike, released
in early 1974. In fact parts such as the swingarm,
rear wheel etc. were identical to the AS-3,
though the CS2 forks, DS6 front brake, DS6 front
wheel, fuel tank and obviously fairing and clip-on
handlebars were changed from the roadbike.
The frame was quite similar to an AS-3 unit,
though produced as a racing special, featuring
different looking top rails and other modifications
such as removal of un-necessary lugs and strengthening
the unit to handle the rigours of a racing environment.
Motor-wise, Yamaha chose to keep the basic
form of the AS-3 cylinders and heads. The only
modifications were altering the porting and
chrome lining the bores, changing the exhaust
securing system to springs from bolts, and also
changing the compression ratio. This combined
with new exhausts, pistons, 28mm carbs, close
ratio gearbox and a Hitachi CDI ignition system
( visually identical to the TZ units ) boosted
the output to a competitive 24bhp at 12,500rpm.
Heavier clutch plates, strengthened crankcases
around the main bearing journals, and the primary
gear being secured to the crankshaft by key/keyway
and nut rounded off the modifications to the
motor. The TA125 was a 5 speed though there
were a few factory 6 speeds around. There were
7 gear kits available, for road use.
Production of the TA 125 ceased in Nov.1974,
marking the end of Yamaha's air cooled 2 stroke
production roadracers and the beginning of a
five year wait for another 125 roadracer, the