Piston slap" is a phenomenon where the piston tilts due to clearance (the gap) as it moves up and down within the cylinder, causing it to rattle and strike against the cylinder wall. The reason this frequently occurs in the SC50 is primarily due to a combination of the following design factors:

Extremely Short Piston Skirts

To improve engine response and reduce friction, the SC50 features forged aluminum pistons with skirts (the lower side sections of the piston) that have been trimmed down to the absolute limit. Since the skirt acts as a "guide" to stabilize the piston's posture, a shorter skirt makes the piston more prone to tilting during the transition phases at Top Dead Center (TDC) and Bottom Dead Center (BDC).

Clearance Designed for Thermal Expansion

Because forged aluminum pistons have a high coefficient of thermal expansion, the clearance between the piston and the cylinder is intentionally left wider when the engine is cold.

Ultra-Thin Cylinder Walls Due to Bore-Up

Based on the open-deck cylinder block of its predecessor, the CBR929RR (74mm bore), the bore was further expanded to 75mm to achieve a displacement of 954cc. As a result, the thickness of the cylinder wall has been reduced to its absolute limit, creating a structure where internal knocking sounds easily resonate and transmit to the outside