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Also a transmission has to be designed correctly. On the one hand, this is the right choice with regard to the transmission ratio of the individual gears as well as the determination of the best functioning primary gear ratio.

worb5 vespa lambretta gearing

The decisive factor is the applicable power, the total weight of the driver with the vehicle and the acceleration or final speed to be achieved or desired. All this can only be estimated before engine mounting. Often one is in the selection of the translation next to it and complains gear connection and / or too little final speed.
In the case of measurements on km / h on our performance test, it is quite clear whether the overall gear ratio was selected too short or too long in the last high gear.

worb5 vespa lambretta gearing

The picture above shows that the theoretical first BLUE measurement of the final speed is at approx. 110 km / h - with an available power of 30 hp.

That means the translation is much too short. With 30 hp rear-wheel drive it is possible to drive safe 130 to maximum 150 km / jh.

The RED measurement shows the same motor with a different primary ratio. 140 km / h can also be achieved with the long-term translation without losing any significant acceleration.
Gear leap
Just tuned engines fight with the so-called gear jumping. The gear flies out under load (during acceleration).
In the Vespa PX series, a modern LUSSO gearbox with the appropriate LUSSO gear shift must be installed. The additional use of a reinforced switching spring is also conceivable.
With Vespa Smallframe models, it is useful to use a hardened and well-machined DRT shift claw with a slightly reinforced shift spring. Even with a bit higher performance, all 4 gears should be replaced by DRT gear wheels.
Lambretta engines require a high-quality gear shift claw with original spring or a very slightly reinforced shift spring.

worb5 vespa lambretta gearing
worb5 vespa lambretta gearing

For all gearboxes a good and correct assembly is a prerequisite for perfect operation.
The gearbox must be adjusted properly and the gears should be sorted right around, which is sometimes not easy for the layman.

worb5 vespa lambretta gearing
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