Straight-toothed FAIO / EGIG PERFORMANCE primary sprocket for high-performance Vespa small-frame engines, such as those equipped with an EGIG 220 or Quattrini M200.
The straight-toothed FAIO / EGIG PERFORMANCE Z50 primary sprocket was developed for high-performance Vespa small-frame engines. It can be combined with the corresponding 20- or 21-tooth primary sprockets, enabling two long primary gear ratios for high-torque engines such as the EGIG 220 or Quattrini M200.
The low total number of teeth compared to conventional small-frame primary drives is a key design feature of this system. With the same center distance, fewer but significantly larger teeth can be used. This creates strong tooth bases and durable tooth flanks capable of withstanding the high forces generated by modern small-frame engines.
FAIO / EGIG PERFORMANCE Z50 straight-toothed Z20 or Z21 for powerful small-frame engines
The primary sprocket can be combined with two different primary pinions. This allows the final drive ratio to be specifically tailored to displacement, torque, RPM range, gear ratios, tire size, and intended use.
| Primary pinion | Primary sprocket | Ratio | Character |
|---|---|---|---|
| Z20 | Z50 | 2.50 | The shorter of the two combinations, with slightly more pulling power and a smoother transition |
| Z21 | Z50 | 2.38 | Very long primary gear ratio for high-displacement, high-torque engines |
Calculation: Number of teeth on the primary sprocket divided by the number of teeth on the primary pinion. A higher number corresponds to a shorter primary gear ratio.
With the 20/50 and 21/50 combinations, this primary sprocket covers a particularly wide gear ratio range. Such gear ratios are intended for engines that generate sufficient torque even at comparatively low RPMs to smoothly handle the long primary gear ratio.
High-displacement engines in particular, such as the EGIG 220 or Quattrini M200, can benefit from a long gear ratio. With the appropriate transmission gearing, engine speed decreases at cruising speed, while the available torque can still be utilized for powerful acceleration.
A particularly long primary gear ratio is not automatically the best choice for every setup. The design must match the usable RPM range and the gear ratios.
Conventional Vespa small-frame primary gear ratios often use significantly higher tooth counts. FAIO and EGIG PERFORMANCE take a different approach: The gear pair has fewer, but larger, teeth.
Given a fixed center distance, the reduced total number of teeth allows for a larger tooth geometry. This results in more material in the tooth root and a correspondingly strong tooth flank. This is particularly advantageous for high-displacement engines, as the individual teeth are subjected to considerable stress during acceleration and load changes.
The primary gear has straight teeth. Unlike a helical primary gear set, this prevents the generation of axial tooth forces that would place additional lateral stress on the coupling, bearings, and retaining elements.
The force is transmitted directly via the tooth flanks. This makes straight-toothed designs particularly suitable for high-performance motors. Operating noise depends largely on tooth geometry, manufacturing quality, tooth flank clearance, and assembly.
In the conventional system, the primary pinion is mounted on the cone of the secondary shaft. Power is transmitted via the frictional contact between the two tapered surfaces. To ensure that this frictional connection functions reliably even at high motor torque, the mounting nut must be tightened to a sufficiently high torque.
When the tapered connection is correctly assembled, the disc spring—often referred to as a half-moon spring—does not transmit the motor torque. Its primary function is to position the primary pinion and prevent it from rotating on the taper when the nut is tightened.
To generate the necessary frictional engagement on the cone, tightening torques of up to approximately 90 Nm may be required, depending on the design. This high torque acts on the comparatively narrow thread of the auxiliary shaft.
In the polygonal design, torque is not transmitted via the frictional engagement of a cone. The primary pinion and housing engage with each other via a form-fit using a suitably shaped polygonal profile.
The retaining nut must therefore primarily secure the pinion axially. It does not need to generate the frictional fit required for torque transmission through a very high tightening torque. As a result, the required tightening torque can be significantly reduced compared to conventional conical fastening.
The specified tightening torque must always be adhered to in accordance with the manufacturer’s instructions for the polygon components used.
High-displacement small-frame engines place significantly greater demands on the primary drive than a standard Vespa engine. In addition to sheer engine power, the primary pinion and primary sprocket are subjected to high torque, severe load cycling, and rapid changes in RPM.
The FAIO / EGIG PERFORMANCE Z50 primary sprocket is particularly well-suited for engines that provide sufficient torque for a long primary gear ratio. Typical applications include the EGIG 220, Quattrini M200, and comparable small-frame setups with high displacement and torque.
Within the FAIO / EGIG PERFORMANCE system, primary sprockets with 50 and 52 teeth are available. The two versions are combined with different primary pinions, thereby covering different gear ratio ranges.
| Primary Sprocket | Possible primary pinions | Gear Ratio Range | Basic Characteristics |
|---|---|---|---|
| Z50 | Z20 or Z21 | 2.50 or 2.38 | Wide gear ratio range for high-torque motors |
| Z52 | Z17, Z18, or Z19 | 3.06 / 2.89 / 2.74 | Shorter and more versatile gear ratio range |
The primary gear and primary pinion must be selected from their respective tooth count ranges. The Z17, Z18, and Z19 pinions are designed for the Z52 primary gear and are not compatible with this Z50 primary gear.
The Z50 primary sprocket may only be combined with the designated straight-toothed FAIO / EGIG primary pinions with 20 or 21 teeth.
The key factor is the Vespa small-frame engine used and its primary drive. The vehicle specification alone does not confirm that all required FAIO or EGIG components have already been installed.
| Manufacturer | FAIO / EGIG PERFORMANCE |
|---|---|
| Component | Primary Sprocket |
| Number of Teeth | 50 teeth |
| Tooth Profile | Straight-toothed |
| Matching primary pinions | Z20 and Z21 |
| Possible gear ratios | 2.50 and 2.38 |
| Vehicle range | Vespa Smallframe |
| Models | V50, PV125, ET3, PK50, PK80, and PK125 |
| Typical engines | EGIG 220, Quattrini M200, and comparable high-performance small-frame engines |
| Special Feature of the Gear Teeth | Large tooth geometry achieved by reducing the total number of teeth in the gear pair |
| Advantage of the polygonal pinion | Positive-lock torque transmission with reduced tightening torque and lower stress on the auxiliary shaft thread |
The FAIO / EGIG PERFORMANCE Z50 primary sprocket, when paired with the Z20 and Z21 pinions, offers two long primary gear ratios for Vespa small-frame engines with particularly high torque. The reduced total number of teeth allows for a robust tooth geometry with a wide tooth base and durable flanks.
When paired with a compatible Poligon primary sprocket, engine torque is transmitted via a positive-lock engagement. Unlike with a conventional conical mounting, the necessary positive engagement does not have to be achieved via a tightening torque of up to approximately 90 Nm. This reduces the required tightening torque and protects the comparatively slender thread of the secondary shaft.
DE | €
