Maxsym MC4 500cc racing engine
Features and benefits
Cycle4-stroke for low emissions and improved fuel consumption
Configuration2 cylinders in line for minimum weight and package size
ConstructionMonoblock cylinder head – This reduces weight and eliminates the need for a head gasket and greatly reduces the cylinder bore distortion normally caused by the head bolts. The coolant jacket around the combustion chamber is also superior to a standard cylinder head design. Removable, Nicasil coated aluminium liners allow worn bores to be replaced at minimum cost.
Horizontally split crankcases – This gives the most rigid structure and most straightforward method of manufacture.
Cassette gearbox – The complete gearbox assembly can be removed without the need to strip the engine, this allows ratios to be changed for different circuits easily.
CrankshaftOne-piece steel forging of unique, proprietary design. The design allows maximum pin overlap giving exceptional stiffness with minimum weight. All bearings are conventional plain shell bearings.
BalancerMaxsym’s proprietary system – This fully cancels both primary and secondary inertial vibration forces giving an exceptionally smooth running engine.
Piston/con rodForged aluminium pistons with 2 rings and 2 piece titanium con rods follow conventional racing 4-stroke practice.
Valve gearAll gear cam drive gives accurate timing and best durability at ultra high speeds. The cam drive is, unusually, taken from the clutch gear, thus reducing parts count and weight. The valves, 4 per cylinder, are titanium and are controlled by conventional, multi rate steel springs. Double overhead camshafts act directly on bucket tappets. A brake hydraulic pressure controlled slave cylinder operates a decompression system (acting on 2 exhaust valves) to reduce engine braking to a level similar to a 2-stroke engine.
CoolingLiquid with Maxsym’s unique monoblock cylinder head design.
LubricationMaxsym dry sump system including multi-stage scavenge pumps and mechanical centrifuge to reduce oil foaming. The oil tank is located under the engine to avoid drain down and give the neatest package.
Gas exchangeA 2 shaft contra-rotating barrel throttle gives accurate, progressive control and zero restriction when fully open. The inlet ports are situated at the front of the engine and the exhaust at the rear. This allows maximum room for the air box, with easy access to cool air, and a straight route for the exhaust system.
TransmissionA conventional dry clutch, with primary drive by gears, drives 6-speed sequential, cassette gearbox. The gearbox has a separate oil circuit to the engine, ensuring maximum durability and allowing different oils to be used.
IgnitionSingle central spark plug per cylinder, CD ignition system
Fuel system4 off pintel injectors mounted in bellmouths. Fuel and ignition controlled by 32 bit 33MHz ECU monitoring engine speed, throttle position, manifold pressure, coolant/air inlet temperatures and combustion knock. Software features include wideband lambda air/fuel ratio control, data logging and telemetry.
Technical specification and performance
Bore/stroke86 x 43 mm
Capacity500 cc
Compression ratio17.0:1
Max. power82 kw (110 bhp) @ 15,000 (predicted)
Max. torque54.4 Nm (40.1 lbs.ft) @ 14,000 (predicted)
Engine weight30 kg (inc transmission)
Package size340mm H x 235mm W x 265mm L