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Two & Four Stroke Hybrid Developed

It’s one of the Holy Grails of motorcycling – finding an engine which combines the compactness, simplicity and power of a two-stroke with the better manners and cleaner running of a four-stroke. Swedish engineer John Ellwood claims to have designed a two/four-stroke hybrid which works.

He’s developed a 1298cc single (yes, you read that right) which uses elements of both two- and four-stroke technology to produce a claimed 150bhp at 6000rpm. Although still working on a four-stroke principle (suck, squeeze, bang, blow) it has two-stroke style crankcase induction, the charge compressed in the crankcase on the power stroke, then held by three reed valves, passing through a massive intercooler before it enters the combustion chamber. The cylinder head has a valve, but unlike the poppet valves and springs of a conventional four-stroke (Ducati desmos excepted) it uses a single rotary valve to control induction, ignition and exhaust phases. It’s belt driven from the crankshaft.

Is all this complication worth the effort? Well, Ellwood has form, having been building engines like this since 1994, successfully racing his previous 500cc two/four-stroke hybrid – the 1300 has been given permission to compete in Supermono.

Jim Freeman, Chair of the BMF, said: “Just when I thought that ICE development was dead, along comes this. Something tells me that it will most likely become a footnote to the ICE story, but interesting anyway.”

Written by Peter Henshaw

Top image courtesy of Ride Apart