The CY 36mm bore 2-bolt cylinder.

Race Porting offered, HT.

Championship Porting offered, HT.

2mm stroked crank with head modifications offered, (30.5cc)

Reed case porting offered, single boost port.

HP; 6.25 to 6.90

(Champ ported “HT“, stock stroke crank 28.5cc top end kit, 6.3 HP)
(Champ ported HT, 2mm stroked 30.5cc top end kits; one with 2mm crank, and one with out a crank, 6.5 HP)
(2mm stroked 30.5cc top end kits, not ported. One with a 2mm crank and one with out a crank, 4.8 HP)
(Race Ported, stock stroke GP290 top end kit, 6.0 HP)