Vortex RSZ and RTZ engines are the newest engines for KZ shifter karts from Vortex. The difference between the two is the length of the connection rod. RSZ: 110 mm and RTZ: 115 mm. The new Vortex KZ RSZ and RTZ motors biggest news is the design of the crankcase. Find all the new parts for Vortex RSZ and RTZ underneath. We sell all spare parts for Vortex KZ engines RSZ and RTZ both gearbox, crankshaft, speed shifter, clutch, exhaust, carburettor, reed valve, and cylinders and pistons.