Kyosho SX040 Idler Gear Shaft Scorpion XXL

This is the idler gear shaft for the Kyosho Scorpion XXL.

An idler gear sits between two other gears in a transmission to transfer drive across a gap or to reverse the direction of rotation, and the idler shaft is what it turns on. That makes the shaft a precision part rather than a simple pin: its position sets the gear mesh on both sides of the idler, and it has to hold that position while carrying full drivetrain torque.

Wear here has knock-on effects. A worn or bent idler shaft lets the gear wander out of true, which changes the mesh as it rotates. The gearbox runs noisy, the tooth faces wear unevenly, and eventually the gears begin to strip. Because the symptom presents as gear noise, most people replace the gears first and are then surprised when the noise returns.

This is the genuine Kyosho part, so the idler sits exactly where it was designed to and your gear mesh returns to correct. Always check mesh after fitting. It fits the 1/7 scale Scorpion XXL in both electric and nitro forms.