by [email protected] | May 11, 2026 | Performance Guides
Rejetting the carburetor is a required step after any performance modification on a Chinese 50cc scooter. A lean engine is a damaged engine. This guide covers reading the spark plug, choosing the right main jet size for your specific mods, and dialing in the mixture...
by [email protected] | May 11, 2026 | Performance Guides
A performance exhaust is one of the most effective and affordable upgrades for a Chinese 50cc scooter. The stock exhaust is heavily restrictive — a free-flowing performance exhaust releases that restriction and noticeably improves power. This guide covers the full...
by [email protected] | May 11, 2026 | Performance Guides
Upgrading the clutch springs on a Chinese 50cc scooter delays engagement to higher RPM, keeping the engine in its power band longer for improved acceleration. This guide covers the complete clutch spring swap on a QMB139 engine. Tools Needed Clutch puller toolSocket...
by [email protected] | May 11, 2026 | Performance Guides
Dr. Pulley sliding weights are one of the best bang-for-buck upgrades for a Chinese 50cc scooter. This guide explains the difference between sliders and round rollers for the QMB139 engine, how to choose the right 16×13 mm gram weight, and how to install them....
by [email protected] | May 11, 2026 | Performance Guides
Roller weights are one of the best and cheapest CVT performance upgrades for a Chinese 50cc scooter. The QMB139 uses 16×13 mm roller weights — different from the GY6 150cc. This guide explains how to choose the right weight for your riding style and how to...
by [email protected] | May 11, 2026 | Performance Guides
A performance variator upgrades the CVT ratio spread on a QMB139 50cc scooter for better acceleration and higher top speed. The swap takes about an hour and uses basic tools. This guide covers confirming compatibility, removal, installation, and tuning. Tools Needed...
