A motor with definitely advanced linear power without any more brusque reactions. Optimised output at all speed rates, especially at low and medium speed. Absolute performance. These are the main characteristics of the two new Polini Motori kits for Honda CRF 450 4S cross, enduro, motard. These new Polini thermic groups are sure to meet the needs of all racers and fans, whatever the conditions. The two new Polini kits feature a 96 mm bore like the original or 101 mm bore. Both are fitted with the exclusive "MLS" (Multi Layer Steel) head seal, made from stainless steel with fluoridated technopolymer coating for max heat resistance. Cast high strength aluminium alloy piston. Complete with special nitrided chrome-plated steel segment. The oil scraper section is especially thin to keep friction down. The new thermic groups are made from a specific cast aluminium light alloy for off-road and motard competitions. The cylinder has a "Closed Deck" system for internal flow of the coolant. This increases the thermal stability of the cylinder, cutting any barrel distortion. The kit with an original 96 mm bore and standard output of 449.4 cc has the same compression ratio as before. It offers excellent value for money and is a valid alternative to original spare-parts. The kit with the larger 101 mm bore takes effective output to 497.5 cc. Absolutely top performance "racing" distribution map. Designed and developed specifically for track racing needs. The barrels in both kits are nickel-silicon coated for smoother piston movement. No structural or mechanical problems envisaged. Better resistance to friction. Improved heat dissipation. Constant mechanical tolerances all the time.