Cvk Main Jet (# 138) for Scooters & Mopeds

Cvk Main Jet (#138) for 139QMB and GY6 Scooters

The Cvk Main Jet (#138) is an accurately made part built for scooters and mopeds that use 139QMB and GY6 engines. Fitting a new one helps the fuel flow correctly and can make the engine run better. It belongs to the scooter carburetors & jets range and has a key job in how the bike runs. It works with a range of CVK carburetors that take a 5mm main jet.

Jet Specifications

This main jet uses a Keihin round design, which is a dependable choice for performance setups. It has an M5x0.80 thread and measures 8mm overall in length, so it sits properly in the carburetor slot. Getting the jetting dialed in may take some testing before you find what works best for your particular setup.

When to Replace Your Main Jet

Consider swapping the main jet if the throttle feels slow to respond, the idle is uneven, or you have changed something on the engine that could alter fuel flow. Keeping up with routine maintenance and correct jetting helps your scooter stay smooth and efficient.

Specifications

• Type: Main Jet
• Thread Size: M5x0.80
• Overall Length: 8mm
• Fits: 139QMB/GY6 50cc and 80cc engines and 157QMJ/QMK/QMI 125cc, 150cc

Fitment

Fits:

• 139QMB-based 50cc and 80cc engines (engine codes 139QMA, 139QMB, 1P39QMB, 1P39QMA-2, YN139QMB, JJ1P39QMB, 139FMA-2, BD1P39QMB, BN139QMB, 147QMD, other QMA and QMB models)
• 157QMJ-based 125cc, 150cc and 169cc engines (engine codes 157QMJ, 161QMK, 152QMI, 1P61QMK, YN1P57QMJ, 1P52FMI, 154FMI, JJ157QMJ, 1P57QMJ, BN157QMJ, BN161QMK-A, other QMJ, QMK and QMI models)
• Any engine with a code containing QM or FM and a 5mm main jet slot CVK carburetor

How to choose: Make sure the 5mm main jet slot on your CVK carburetor and the M5x0.80 thread both match; this jet is 8mm overall length.

Shop more: Browse Scooter Carburetors & Jets · Browse Scooter Parts