Primary sprockets for Vespa Smallframe – for adjusting the gear ratio on more powerful engines.

Primary gear ratios are the most common way to change the gear ratio of a Vespa Smallframe. Installation makes sense for all cylinders 75 cc and larger. As a general rule: The more powerful the engine, the longer the gear ratio should be compared to the original.

Primary Driven Gears lengthen all gears. They consist of a Primary Driven Gear and a primary sprocket and are almost always straight-toothed. This gives them lower power loss and higher efficiency than helical-toothed primary gear ratios. In addition, the bearings are subjected to less radial stress. If you don’t want to completely disassemble the engine for this, you can simply install a different Primary Driven Gear. The cylinder classes listed are good, proven guidelines.

The gear ratios from SIP PERFORMANCE and RMS offer excellent value for money. The primary sprockets from OLYMPIA and FERODO are somewhat more robustly constructed; SURFLEX is often preferred by DRT riders. The gear ratios from POLINI fill the gaps between the standard sizes. The high-quality aluminum primary sprocket also provides additional weight savings.

Conclusion: There is hardly a more effective way to adapt the gearbox to increased engine power.