FAIO / EGIG PERFORMANCE straight-toothed 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 Z52 primary sprocket was developed for high-performance Vespa small-frame engines. It can be combined with the corresponding primary sprockets featuring 17, 18, or 19 teeth, enabling three practical primary gear ratios for high-torque engines such as the EGIG 220 or Quattrini M200.
The unusually low number of teeth on the corresponding primary sprockets 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 Z52 straight-toothed Z17 to Z19 for powerful small-frame engines
The primary sprocket can be combined with three different primary sprockets. This allows the overall gear ratio to be adjusted to suit engine displacement, torque, RPM range, gear spacing, and intended use.
| Primary pinion | Primary sprocket | Ratio | Character |
|---|---|---|---|
| Z17 | Z52 | 3.06 | Shortest combination with high tensile strength and close pitch connection |
| Z18 | Z52 | 2.89 | Balanced ratio between acceleration and final drive ratio |
| Z19 | Z52 | 2.74 | Longest combination for engines with correspondingly high torque |
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 overall gear ratio.
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, this design generates no axial forces that 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 attractive 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 a cone. Power is transmitted via the frictional contact between the two conical surfaces. To ensure that this frictional connection functions reliably even at high motor torque, the mounting nut must be tightened to a correspondingly high torque.
When the conical 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 cone 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 secondary shaft.
In the polygonal design, torque is not transmitted via the frictional fit of a taper. The primary pinion and housing engage in a positive fit via a precisely shaped polygonal profile.
The fastening nut must therefore primarily secure the pinion axially. It does not first 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 actual specified tightening torque must always be adhered to according to the manufacturer’s specifications 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 above all to high torque, severe load cycling, and rapid changes in RPM.
The FAIO / EGIG PERFORMANCE Z52 primary sprocket is therefore particularly suitable for engines where a conventional primary drive reaches its load limits. 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 |
|---|---|---|
| Z50 | Z20 or Z21 | 2.50 or 2.38 |
| Z52 | Z17, Z18, or Z19 | 3.06 / 2.89 / 2.74 |
The primary gear and primary pinion must be selected from their respective tooth count ranges. A Z20 or Z21 pinion is intended for the Z50 primary gear and not for this Z52 primary gear.
The Z52 primary gear may only be combined with the designated straight-toothed FAIO / EGIG primary pinions with 17, 18, or 19 teeth.
The key factor is the Vespa small-frame engine used and its primary drive. The vehicle specifications alone do not confirm that all required FAIO or EGIG components have already been installed.
| Manufacturer | FAIO / EGIG PERFORMANCE |
|---|---|
| Component | Primary Sprocket |
| Number of Teeth | 52 teeth |
| Tooth Profile | Straight-toothed |
| Matching primary pinions | Z17, Z18, and Z19 |
| Possible gear ratios | 3.06 / 2.89 / 2.74 |
| 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 Z52 primary sprocket, when paired with the Z17, Z18, and Z19 pinions, offers three gear ratios for high-performance Vespa small-frame engines. 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, torque is transmitted via a positive-lock engagement. Unlike with a conventional tapered mounting, the necessary positive locking 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 fine thread of the secondary shaft.
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