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49cc/4 stroke and 150cc/4 stroke
Transmission Step-Up Kit (faster off-the-line response): Perhaps one of the most common complaints people have with motor scooters (particularly 4 stroke motor scooters) is the relatively slow take-off speed from a dead stop. This is due mostly to the gearing mechanism combined with the time it takes for a 4 stroke engine to rev-up. We have developed a transmission STEP-UP kit specifically for the 139QMB 4 stroke/49cc Engine (and clones) and for the 157QMJ (gy6) Engines (and clones). The kit will dramatically improve the take-off speed from a dead stop. The kit consists of a set of custom rollers for the variator and a CD with detailed installation and tuning instructions.
Upgrading Roller Weights in the variator is the simplest of upgrades and the least expensive for the consumer. The main rule for tuning variators is: the lighter the roller the more rpms are needed to push the rolls outwards through centrifugal motion to set the gear change in motion. Heavier roller weights need lower rpms to start moving. Heavier roller weights = slower take off speed, more acceleration, = higher maximum speed. Lighter roller weights =faster take off speed, less acceleration = lower achievable speed. The right balance is an individual choice, for daily use a driver might prefer lighter weights for more power to take off faster at a stop light.
ABOUT THE CUSTOM ROLLERS...
These sliding rollers perform up to 20% better than standard round weights and last up to 18% longer with 22% less performance material loss. The weights have several unique features such as their composite material being nylon for faster performance.
* Made of unique tribological material SL-9T and SL-9TS (oilless PA46) * Low friction coefficient / Low wear / High temperature resistance * Aluminum compatible; No abrasive fibers (glass fiber or carbon fiber) * Fastest Roller Weights available
While it can be installed by the consumer, it is not recommended unless you are familiar with small engines and have access to an impact wrench.
18 X 14 for GY6 150cc engines in scooters and go carts. 16 X 13 for QMB139 50cc engines
Heavier roller weights= A slower take off speed with more acceleration and a higher top speed.
Lighter roller weights = A faster take off speed with less acceleration and lower top speed.

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