Cooling System and Water Flow

A lot of thought went into the elaborately designed cooling system as well. The GP90’s well-thought-out water flow ensures constant temperature of the cylinder and good heat dissipation exactly where it is necessary. The outlet was equipped with extra cooling fins (inside the cylinder) to guarantee optimum cooling. The 3-part anodized green cylinder head, CNC-milled from AW6062, is an essential part of the cooling system. With an additional liner, very hot water is redirected from outlet to inlet resulting in stable temperature of all parts of the cylinder. On top, there’s no denying that this part is a real looker!

3-Part Exhaust Port

The exhaust port of the MXS GP 2 90cc cylinder is divided into 3 ducts, a main port accompanied by so-called boost ports. This port design has 2 distinct advantages when compared to standard “bridged” port design.

The Bridged Exhaust Port: Heat dissipation of the bridge of a bridged exhaust port is rather poor; it tends to overheat in the middle as heat cannot be distributed to top and bottom. The result: it has to be ground down on a regular basis to avoid piston seizure at the piston ring. In contrast, the 2 boost port bridges can dissipate heat much better as they are simply shorter. No need to grind, which benefits piston and piston ring. This will result in longer life at same rpm.

Patented Mounting System

Gas flow volume and speed depend on size and shape of the transfer ports. In standard cylinder design, port layout is usually limited by the location of the cylinder stud bolts – they vertically protrude the entire cylinder. The new, patented mounting system for the MXS GP 2 90cc cylinders is using locking pins instead of stud bolts. The limitation caused by the spacing of the stud bolts is bypassed and the path is clear for optimum port design. As a result, this cylinder kit will yield performances unheard of in this field. This cylinder design is not common in 50cc tuning as it is relatively difficult to devise a well-done 3-part exhaust port for cylinders with more than 50cc displacement. Our new system with locking pins provides a solution to this problem.

Function of boost ports: the gas flow is released back into the cylinder (looped) and can be directed in a much more controlled way to where it is meant to go. At the same time, this “looped” charge is not prone to overheating as it is with a standard bridged port (as the shorter boost bridges do not heat up that much).

Combustion chamber

The MXS GP 2 90cc cylinder kit includes a standard bathtub-shaped combustion chamber used in modern high-performance 2-stroke engines. Compression ratio is 15:1.