Crankcase designed for high performance

The crankcase of the 306 ccm BFA engine is based on a newly developed casting mold. The shaft spacing and basic design of the powertrain remain the same and correspond to the original PIAGGIO design. Around this basic shape, BFA has created plenty of space: for a stronger Crankshaft with greater stroke, for the Cylinder with a 78 mm bore, for the generously shaped transfer ports, and for thicker walls and reinforcements.

The cylinder stud spacing is 100 x 100 mm. The solid seating for the Input Shaft is particularly noteworthy. The inlet to the crankcase is located directly across from the cylinder base, spans both halves of the crankcase, and provides 70 mm of width for the Reed Valve.

Both crankshaft bearings have an outer diameter of 62 mm. On the clutch side, the crankshaft is supported by a cylindrical roller bearing; the fixed bearing is located beneath the Ignition system. The Oil Seals used are 25 x 35 x 7 mm and 25 x 40 x 7 mm. The Intake Manifold and Reed Valve are not included with the Crankcase.

Cylinder with a 78 mm bore

The centerpiece of the BFA 306 engine is the completely redesigned cylinder. It achieves its unusually large displacement through a 64 mm stroke and a 78 mm bore. The piston is a flat-top piston with a single Piston Ring. The cylinder head is secured with eight fittings; the Spark Plug is centrally located and sealed with an O-Ring.

Gas exchange takes place via 5 overflow ports and a 3-way exhaust port. The exhaust flange is made of steel and is secured to the Cylinder with 4 Screws. The outer connection diameter is 50 mm. The cylinder studs are not through-bolts; the cylinder is fitted at the base. This provided the designers with a great deal of space when designing the ports.

Heavy-duty crankshaft with toothed clutch stub

The crankshaft of the BFA kit is particularly robust, with a width of 54.4 mm and a diameter of 102 mm. The polished forged connecting rod is 135 mm long. The most striking feature of the crankshaft is the clutch stub: The clutch is not simply secured against rotation with a Woodruff Key, but is pushed onto a sturdy toothed spline. On the alternator side, flywheels with the original Cone can be installed.

5-washer clutch for heavy-duty use

The Clutch designed by BFA for the 306 ccm engine is connected to the BFA Crankshaft via a toothed engagement to prevent rotation. It is based on the PX Clutch from the BFA lineup. The operating principle of the Vespa Largeframe clutch has been reversed. This is intended to reduce the mass rigidly connected to the Crankshaft. At the same time, it is designed to improve the break-in behavior, reduce jerking when pulling away, and provide a more responsive feel overall.

The primary pinion is custom-made for this Clutch. Its flat design frees up installation space—an important requirement for accommodating five friction plates within the Clutch. The Clutch Pinion is connected to the CNC-milled outer aluminum cage via 12 Screws. On the inner shaft, the Clutch is mounted on a Needle Bearing instead of the original bronze bushing. The Pressure Plate is also equipped with a Bearing that sits in a machined aluminum component.

All friction plates and Cover Plates in the Clutch assembly are made of aluminum. The bottom plate houses 6 springs—similar to a small-frame Clutch—which can be supplemented with 6 additional small springs. The package includes a straight-toothed primary gear set. It also includes two Screws that can be used to compress the Clutch and allow for replacing the friction plates while the Clutch is installed. The entire assembly fits under the original PX 200 Clutch Cover.

Exhaust Designed for the 306 cc Concept

The exhaust system for the BFA 306 engine was also designed specifically for this engine. It not only fits the cylinder’s exhaust flange but was engineered to match the displacement, valve timing, and exhaust port cross-sections. This results in a powerful and harmonious power curve.

High-End for Vespa Largeframe

The BFA 306 engine and the individual parts of the kit are among the most exclusive products available for classic manual-shift scooters. This applies not only to the price. The quality of materials, workmanship, and technical design are also of the highest standard. Above all, however, the performance made possible by these components represents the absolute pinnacle—and all within the installation space of the original Vespa Largeframe engine.

Technical Specifications

• Displacement: 306 ccm
• Cylinder stud spacing: 100 x 100 mm
• Intake: Diaphragm intake transverse to the cylinder base
• Diaphragm width in casing: 70 mm
• Crankshaft bearings: 62 mm outer diameter
• Oil seals: 25 x 35 x 7 mm and 25 x 40 x 7 mm
• Stroke: 64 mm
• Bore: 78 mm
• Cylinder: Aluminum
• Cylinder Head: 8-fitting
• Overflow ports: 5
• Exhaust: 3-piece
• Exhaust flange: Steel, secured with 4 Screws
• Outer diameter of exhaust port: 50 mm
• Crankshaft: 54.4 mm wide, 102 mm diameter
• Conrod: polished forged conrod, 135 mm
• Clutch: 5-washer clutch
• Clutch Basket: CNC-machined aluminum basket
• Clutch Pinion: secured with 12 Screws
• Springs: 6 springs, expandable with 6 small additional springs

Conclusion: The BFA 306 engine is the most sophisticated way to give a sheep’s clothing a wolf’s heart.

These products are a perfect match – SIP TIPS:

• Sturdy transmission, e.g., with DRT F1 components
• Modern ignition system, e.g., SIP PERFORMANCE ignition
• Properly sized carburettor, e.g., KEIHIN PWK 38
• Be sure to order bearings, Oil Seals, and Rubber Engine Mounting Bushes at the same time