Lambretta Gearing

The Lambretta gearbox is almost identical between models following the LD models. Most Series 1-3 gearboxes will fit in other model bikes making a huge range a varied gearbox ratios available.

Below is an overview of a typical Lambretta gearbox.

  1. The Crank Sprocket - Part 1 of the primary drive: This came as in two standard sizes: 18 tooth used on GP200s and 15 tooth used on all other models.
  2. The Chain - Part 2 of the primary drive: This runs in an oil bath and is basically two chains side by side as one. GP200s use 82 link chains and all other models use 80 link chains.
  3. Clutch Bell - Part 3 of the primary drive: This actually spins independently of the transmission when the clutch is pulled (clutch not shown). It was available in 47 tooth for GP200s and 46 tooth for all other models.
  4. Main Gear Cluster - This is a cast and machined part with integral gears and can only be changed along with the free gears as a unit (there are some exceptions).
  5. Free Gears - These gears turn on a layshaft (6) and each one is selected independently to give the final drive ratio. Neutral is when the selector is in a special gap between the 1st and 2nd gears.


The Primary Drive

This is where the Lambretta gearbox is more flexible then the Vespa gearbox. Both the clutch bell and the crank sprocket can be changed independently of each other. A special chain will have to be used if you vary from the 47/18 GP200 set up or the 46/15 of all the other models. Companies like WCLW sell chains with extra links in them to accommodate almost any variation of front and rear sprockets. They also sell aftermarket front sprockets ranging from 13 to 22 teeth.

The Standard Gearbox

Each model came with a very specific group of four free gears and a single piece main cluster gear. Although these may be shared by different models they are always installed in pairs to be sure that each gear has a meshing counterpart. There are exceptions to this rule which we will add to the gearing calculator once we are sure the information we have is correct.

This is where the fun (or the headache) begins. All these items can be switched out with other model parts or aftermarket parts to achieve a huge range of gears. To make things easier my brother and I created a gear calculator which includes all the standard gearboxes and aftermarket crank sprockets. This information was found in the Lambretta Manual of Performance and Conversions by Ken Herlingshaw

Next Section -->