DRT 22-Teeth Clutch Sprocket for 64-Teeth Primary Gear - Vespa COSA 2 / VNA-TS / VBA-Super / Rally / PX / PE / Lusso / T5

The gearbox gear drives the clutch assembly (main gearbox gear) to the input shaft in the large Vespa engine. By varying the size or number of teeth in this gear, you can change the main gear ratio of your engine. Changing the clutch gear is the easiest and fastest way to change the overall gear ratio of your engine. The more teeth the clutch gear has, the larger the gear ratio.

The gears for the II COSA clutch are available with 20, 21, 22, and 23 teeth. The 20 or 22-tooth gears fit 125-150cc engines, and the 21 or 23-tooth gears fit 200cc engines without having to replace the primary gear. If the primary gear is also replaced, all clutch gears can be used with both engine sizes. The 65-tooth primary driven gear in the 200cc engine can be combined with 21 or 22-tooth gears, along with the original 23-tooth element. The most popular clutch gear conversion is the 22-tooth version, which allows for improved acceleration through the gears without costly tuning, especially between the 3rd and 4th gears. For VESPA T5 engines equipped with the MALOSSI 172cc cylinder kit, a clutch gear with 21 or 22 teeth has proven suitable. If the 65-tooth driven main gear (from the 200cc engine) is used in a 125-150cc engine, the 200-tooth clutch gear can also be used in the smaller engine.

DRT has also managed to fill the gaps in the number of gear teeth available for the PIAGGIO COSA II clutch gears. DRT produces clutch gears suitable for all primary gear sizes. The result is a significantly quieter and more durable drivetrain. This also extends the overall life of the gearbox and therefore the engine, and also improves transmission efficiency, with more power reaching the rear wheel. The straight-cut gearbox gears with 22 or 24 teeth are designed for use with the POLINI driven primary gear. The primary gear ratio of 2.67 resulting from the gear tooth ratio of 24 teeth on the clutch gear sprocket and 64 teeth on the driven primary gear is the highest conversion primary gear ratio available for the II COSA clutch apart from the Worb5 version of course… The clutch gear sprocket with 23 teeth manufactured by DRT matches perfectly with the PIAGGIO OE driven primary drive sprocket in 125-150cc engines with 67 toothed gears and 68 toothed gears, respectively.

Helpful Hint: All larger models from the VESPA VNA/VNB range up to 1994 can be equipped with the COSA II clutch. Due to the larger size of the COSA II clutch conversion, these 125-150cc models require the existing clutch cover to be modified or replaced with the clutch cover from the 200cc engine and a suitable pressure plate. For this reason, they have been included in the accompanying lists.

Bottom line: A suitable transmission is available for every model included in the accompanying lists.

SIP TIP: Don't forget to order a new clutch holding nut, lock washer, thrust plate, and master cylinder. New clutch friction plates are also recommended when performing this job. With different gear sizes on the input and output shafts, even more experimentation with gear ratios is possible. Wider-section tires are also a popular way to raise the engine's gearing.