Selecting The Rotor - Yamaha YZ125(R)/LC Owner's Service Manual

Table of Contents

Selecting the rotor

If you feel the engine pick up faster depending

on the course condition, you can control it by

changing the rotor to the one with a greater iner-

Standard rotor 5CU-85550-11 0.0004kg•m

2 2 Optional rotor 5UN-85550-00 0.00045kg•m

* Inertial mass: The inertial mass of the body is

proportional to its weight and increases in pro-

portion to the square of the distance between its

rotation center and center of gravity. For the

same weight, a greater distance from its rota-

tion center produces greater inertial mass.

Greater initial mass gives a feeling of greater

torque in response to engine revolutions but is

accompanied by greater pick up resistance.

Engine characteristics are shown below in rela-

tion to each rotor:

9Standard rotor

Engine pickup is faster in the entire engine

speed range.

Pickup is fast at an extremely low engine

9Optional rotor

A feeling of torque is obtained at high engine

A broader power band is felt from mid speed to

9 Engine pick up differs according to the course

condition, rider, the settings, etc. Select a suit-

able rotor by comparing it with the standard

one in operation.

9 It is difficult to be advantageous under all

course conditions with a change in the rotor.

Measure the lap times in accordance with race

points and select a rotor to produce a good

entire balance.

*Inertial mass