1971 YAMAHA RT1MX FACTS
WHAT THEY COST
There are still many DT1s and RT1s in use some 44 years later.
Although not popular with collectors, they are an inexpensive way
into vintage racing. Expect to pay around $1500 to $2000 for a
decent example, which is about double the original $995.
The AT1MX ( 125), DT1MX (250) and RT1MX (360) represented
Yamaha’s motocross lineup.
WHAT TO LOOK FOR
The bodywork was often changed—to the detriment of the bike’s
value today—to incorporate a Preston Petty fender or Vesco gas
tank. The oil-injection system was usually removed also. Collectors
want all of the original stuff, especially the stock GYT expansion
chamber. Aftermarket Bassani or Hooker pipes are not as
valuable as the stock pipe. There is a huge bonus for the original
Speed and Sport at (570) 784-6831 is a good source for older
The piston port engine’s engine cases, transmission,
clutch and ignition were similar to that of its 250cc
sibling. Bore was increased from 70mm to 80mm, and
the stroke was increased from 64mm to 70mm. The
installed GYT kit (Genuine Yamaha Tuning) featured
a center-located spark plug head with higher 7.2:1
compression, a ported cylinder, 34mm Mikuni, and
expansion chamber exhaust. Strangely, it kept the
Autolube system. The result was an impressive 36 horsepower—
six more than the RT1 Enduro model.
Besides the price, the best thing about the RT1MX was the
bike’s reliability. Because Yamaha was entering virgin offroad
territory with the DT1 and RT1, its engineers over-designed
the parts to ensure that there were no weak links. Never a
serious Open-class motocross bike, the RT1MX was a popular
entry-level racer, desert bike and enduro machine. ❏