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General
The gearing of the 4 gear transmissions in Vespa and Lambretta can be chosen individually. Main factor here is the power and - more important – torque at low rpm (important for a good connection between gears).

Vespa PX
Transmission
Typically we use PX 200 transmissions. They have a good gearing ratio and the teeth of the gears are strong enough to transfer high forces. PX 80 transmissions have very small teeth and are not suitable for motors over 18 hp. On top of that the PX transmission is very short – so short indeed that it is not suitable for most applications. Also worth mentioning is the T5 Transmission. It is very similar to the PX 200 Lusso, except the 4th gear is a tad shorter (1 tooth more each). The 4th gear fits into any PX 200 Lusso transmission without further modification. This enables a better connection between the 3rd and 4th gear. (see Onlineshop). Compliant to that you can also fit a PX 125 4th gear into a PX 200 „old“ transmission, which has the same effect, to shorten the gearing and enable better connection between 3rd and 4th gear. (see Onlineshop).

Primary
We use the 65 tooth primary on the 177 and 200 PX200 modifications. If a very big rear tire is used, it is a motor for a sidecar or it is a 166/177 modification we use the shorter 21 tooth clutch. The short 68 tooth primary with a 20 or 21 tooth clutch only makes sense on the T5, since this motor develops most of it’s power at high rpm. In stronger T5 motors the PX200 65 tooth primary may be used with the 21 tooth clutch. (see Onlineshop).

Vespa Smallframe
Transmission
In the Smallframes you can find both 3 and 4 gear transmissions. Of course the better connection between gears is found in the 4 gear transmissions. For the Smallframes we offer a 4 gear transmission from ZIRRI (189 EURO) that has a 49 tooth 4th gear (compare to 46 tooth standard) which is very short! The gear ratio 1st through 3rd gear are the same as the stock transmission. (see Onlineshop).

Primary
Here we offer many options (see Onlineshop).

18/67 = 3.72

21/76 = 3.62

24/72 = 3.00

22/63 = 2.86

27/69 = 2.56

24/61 = 2.54

28/69 = 2.34

We have to state here, that we may have problems obtaining certain primaries due to availability. 3.00 works beautifully with 75 ccm and 112 ccm cylinders. 2.86 fits pretty good with 130 ccm Polini / Malossi cylinders. If the motor is exceptionally strong even the longest primary 2.34 will work.

Lambretta
Transmission
There are 8 different transmissions for the Lambretta. Preferably we use a LI 150 transmission because of the excellent ratios. LI150S (Pacemaker) or Close Ratio Transmission. The shift between 3rd and 4th gear is relatively short in these transmission.

Primary
There is more than 10 different sized primary combinations available (sprockets in the front, chain and sprocket in the back) (see Onlineshop).

You can find a gear ratio chart here:

Lambretta gear chart pdf

Vespa PX 200 transmission:

gearbox_listung Lambretta pdf