Nominal Capacity 248.4cm3

Original Bore 58.0mm

Theoretical Maximum Bore 58.01mm

Stroke 47mm

Volume of Combustion Chamber 12cm3 (Repair Limit of 0.6cm3)

Compression Ratio 11.35 : 1

Cooling System Water

DELL’ORTO carburetor – 1 per cylinder. Carburetor Diameter 22mm.

The carburetor body, slide, needle, atomizer tube and atomizer insert is

to remain as originally supplied and cannot be subject to any

modification. No additions or additional machining, filing, drilling or

polishing etc is permitted to these items, this includes the bore/throat.

"PHBL 22" cast in the housing of the carburetor

"BD" or "BS" stamped in the housing of the carburetor

Atomizer Tube stamped with "266DA" or "264DA"

Needle Stamped with D31 or others as nominated in the future

Slide Marked #30 Only

Other settings in the carburetor are free.

Camshaft Drive Type SOHC Belt

Intake Lift 7.5mm

Intake Opening Duration 268 Degree

Intake Timing Opens 25 Degree BTDC

Closes 63 Degree ABDC

Exhaust Lift 7.5mm

Exhaust Opening Duration 268 Degree

Exhaust Timing Opens 65 Degree BBDC

Closes 23 Degree ATDC

Must be genuine item

Maximum of 1 per cylinder according to the following specification.

Weight 24g

Diameter of Valve Stem 5mm

Diameter of Valve Head 26.5mm

Diameter of Seat 23.5mm

Diameter of Duct 21mm

Must be genuine item

Maximum 1 per cylinder according to the following specification.

Weight 21g

Diameter of Valve Stem 5mm

Diameter of Valve Head 24mm

Diameter of Seat 21mm

Diameter of Duct 23mm

Length between axes of Conrod 84.5mm

Weight of Conrod 185 g

Diameter of Big End 35mm

Diameter of Small End 16mm

Weight of Crankshaft 1720 g

A1 93mm

A2 93mm

B1 32mm

B2 32mm

C1 20mm

C2 32mm

Weight of Piston 145 g Complete

Number of Rings per Piston 3

Neither the engine nor any of it's ancillaries may be modified in any way.

"Modified" is defined as any change in form, content or function that represents

a condition of difference from that originally designed. This is to include the

addition and/or omission of parts and or material from the engine package

assembly unless specifically allowed within these rules. The adjustment of

elements specifically designed for that purpose shall not be classified as

modifications, IE carburetor and exhaust adjustment screws