Motorcycle Engines

Steve Prentice Design worked in partnership with Maxsym Engine Technology from 1998 to 2005 on a wide variety of original motorcycle engine designs.

See also 'Maxsym MC4' page.


Steve Prentice Design were responsible for design and Maxsym for engine build and testing.



These projects were targeted at manufacturers and markets where 2-stroke engines dominated to demonstrate improvements to fuel consumption and exhaust emissions if fuel injected 4-stroke technology were adopted.


Each 4-stroke engine was designed to a strict weight limit to match the 2-stroke engine it would replace. Horse power was similarly matched, something few people thought was possible. The swept capacity of each 4-stroke engine was, of course, larger than the 2-stroke it replaced.

Tests with Californian Air Resources Board (and others) showed typically that fuel consumption halved and hydrocarbon emissions reduced by 98%.

Parallel twin cylinder 1000cc engine






Single cylinder 200cc marine outboard engine


When MotoGP announced changing from 500cc 2-strokes to 990cc 4-strokes Maxsym offered consultancy to teams planning to build their own engines. The regulations gave reduced weight advantages to 2 and 3 cylinder engines and weight penalties for use of 6 cylinders or more.

Steve Prentice Design produced concepts for a range of engine configurations:

  • 2 cyl parallel

  • 2 cyl Vee

  • 3 cyl in-line

  • 4 cyl Vee

  • 4 cyl in-line

  • 6 cyl Vee

  • 12 cyl X

Maximum horsepower could be most readily developed using 12 small cylinders, enough to overcome the weight penalty intended for 6 cylinders.


Arranging 12 cylinders into 4 banks of 3 in an X configuration makes the engine amazingly small and it fits comfortably into GP chassis.


Honda surprised everyone when they launched a 5 cylinder Vee engine that dominated MotoGP for several years.


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