Complete Vespa 300 Big Bore Racing Kit from Malossi.  Includes Cylinder Kit and Malossi V4 Head. Add about 25% more horsepower and start passing people on the Interstate for a change. 

TECHNICAL SPECIFICATIONS

Cylinder

Bore 75.5 mm;
Stroke 63 mm;
Compression ratio 12.5:1.
Material: primary aluminium alloy with a high content of hardened and tempered silicon, cylinder liner with silicon carbide coating in a galvanic nickel die and crossed smoothing with two diamond passages with very limited tolerances.
Machining: on machine tools with high precision numerical control.
Cylinder-piston connection with an allowance of 0.05 mm.
Recalculated and upgraded heat exchange surfaces.
Piston

Ultra compact with 3 rings.
Material: special aluminium alloy with high silicon content, low thermal expansion and a tin facing on the sliding surfaces.
Machining on machine tools with numerical control.
Lightened and reinforced.
Upgraded heat exchange surfaces.
Piston rings

Special rings with high sliding ease and very high mechanical resistance.
I° ring compression in nitrided and chromium steel.
II° special  ring.
Three - piece scraper ring made of chromium plated special steel alloy.
Head

Head made of gravity-fed cast aluminium alloy, tempered and sandblasted, machined within thousandth (mm) tolerances utilizing super precise work cells.
Valve guides designed with new profile, made using a powdered metal sintering process (steel, phosphorous, carbon, copper and manganese).
Valve seats made of cobalt-molybdenum steel alloy characterised by copper infiltration and a special heat/chemical treatment. Increased intake valve - ø 25 mm, made of a special steel alloy and a special heat/chemical treatment.
Increased exhaust valve - ø 22.2 mm and made of Nimonich 80 material (Nickel, Chromium, Titanium, and Aluminium alloy).
Exhaust and Intake valve springs made of Si-Cr oil-tempered and annealed steel, designed to operate optimally under increased loads due to increased engine power.

Fits the Following Models 

VESPA GTS i.e. 300  
VESPA GTS Super i.e. 300  
VESPA GTS Super Sport i.e. 300  
VESPA GTV i.e. 300