Yokomo Z4-309C Aluminum Narrow Pulley & Belt set for YZ-4 — rear belt narrowing kit for YZ-4 4WD off-road cars  [Z4-309C]

Aluminum Narrow Pulley & Belt for YZ-4

The Yokomo Z4-309C kit narrows the rear belt path on YZ-4 4WD off-road models to reduce driveline friction and lighten the rotational load. Designed as an RC-scale accessory, the set targets reduced mechanical loss on low-power setups where keeping the drivetrain efficient matters more than peak torque.

Installation focuses on the rear belt segment: the pulley and belt components replace the stock rear-belt routing parts to achieve a narrower span. Basic mechanical experience is sufficient, the work typically involves access to the rear pulley area, removal of the existing belt components, and careful reassembly with correct belt alignment and tension to avoid binding.

Tuning role: by trimming friction in the belt run, the kit helps the drivetrain draw less power under load, which can benefit stock-class or other regulated low-power categories. It is a targeted drivetrain refinement rather than a source of added power, so consider it as a component-level tuning option when aiming for smoother, more efficient belt drive behavior.

Use the Z4-309C when you want a simple drivetrain tweak to reduce belt friction on YZ-4 platforms; pair it with careful belt alignment and tension checks to maximize the intended efficiency gains.