Yamaha YZ85 combustion chambers

Chamber selection:

Y01 - 6.4cc  Stock
Y02 - 6.0cc (95+ octane)
Y03 - 5.6cc (100+ octane)
Y04 - 5.2cc (105+ octane)

Y105 Big bore 52.5  91+(100 suggested)

Y110 Big bore +2mm Hot Rods stroker crank 4134