Cvk Main Jet (# 108) for Scooters & Mopeds

Cvk Main Jet (#108) for 139QMB and GY6 Scooters

The Cvk Main Jet (#108) is a key component for a range of scooters and mopeds that use 139QMB and GY6 engines. It works with almost any CVK carburetor that has a 5mm main jet slot. The jet helps control engine performance and fuel flow, so it is worth a look among the scooter carburetors & jets available for your machine. Getting the jetting right can take some trial and error, so check any available jetting guides before you start.

Build and Fit Details

This main jet uses the Keihin round design and has an M5x0.80 thread, which keeps it snug inside the carburetor. It measures 8mm overall in length. It suits a broad group of engines, including 50cc, 80cc, 125cc, 150cc, and 169cc units that carry specific engine codes.

Signs It May Be Time to Swap the Main Jet

Consider changing the main jet if the engine runs poorly or if the fuel-air mix needs adjusting to get more power out of it. Checking the jet from time to time can show whether a new one is needed, especially when you are modifying or upgrading the scooter.

Specifications

• Type: Keihin round-style main jet
• Thread Size: M5x0.80
• Overall Length: 8mm
• Fits: 139QMB-based 50cc/80cc GY6 engines and 157QMJ-based 125cc/150cc/169cc engines with a 5mm main jet slot CVK

Fitment

Fits:

• 139QMA, 139QMB, 1P39QMB, 1P39QMA-2, YN139QMB, JJ1P39QMB, 139FMA-2, BD1P39QMB, BN139QMB, 147QMD engines (50cc/80cc)
• Other QMA and QMB engines (50cc/80cc)
• 157QMJ, 161QMK, 152QMI, 1P61QMK, YN1P57QMJ, 1P52FMI, 154FMI, JJ157QMJ, 1P57QMJ, BN157QMJ, BN161QMK-A engines (125cc/150cc/169cc)
• Other QMJ, QMK and QMI engines (125cc/150cc/169cc)

How to choose: Only use this jet with a CVK carburetor that has a 5mm main jet slot, M5x0.80 threads, and an 8mm overall length.

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