Maxsym MC4 GP500 and GP600 engines



Steve Prentice Design worked in partnership with Maxsym Engine Technology from 1998 to 2005.

In 2004 we designed MC4, a motorcycle engine project intended for low volume manufacture in house by Maxsym.




Maxsym MC4 project started as GP500, a proposal to replace 2-stroke 250cc Grand Prix class with 500cc 4-strokes. The concept design we came up with was a very compact engine and gearbox focused exclusively on GP class. It was decided for commercial reasons to expand the target market for the engine, to increase capacity to 600cc and include options as shown below.



MC4 engines were designed in 2 capacities (500 and 600cc) for use in a range of off road and racing vehicles:

  • GP500 - 500cc engine for GP karts and GP race motorcycles, to compete and eventually to replace 250cc 2-stroke engines. 85 - 110 bhp, 14000rpm.

  • GP600 - 600cc engine for Supermoto, racing quads, snowmobiles and jet-skis. 75 - 85 bhp, 11000rpm.

The engines had 2 cylinders in parallel configuration with patented crankshaft and balance systems to eliminate vibration usually associated with twin cylinders. The cylinder heads were reversible to place exhaust or intake at the front. The transmission was 6 speed sequential cassette type with dry clutch or fixed ratio primary reduction (for applications where a gearbox is not required). There were dry or wet sump and electric or kick start options.


MC4 engines could replace 2-stroke engines in many racing formula to help reduce the environmental impact of motorsport through reduced emissions, noise and fuel consumption.

The MC4 engines were launched in Germany at Intermot Munchen show on 15 September 2004 and in UK at Autosport International at NEC Birmingham on 13 January 2005.

Unfortunately Maxsym Engine Technology ran out of funding during the final stages of development. The project was stopped and subsequently Maxsym closed down.

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