All sorts of interesting custom bikes and engine projects are coming out of Sweden all of a sudden, or at least, I’m just coming across them, and John Ellwood thought we might like to see one more, it’s his Ellwood Hybrid, a single cylinder, 4 stroke with reed valves, from a 2 stroke, mounted on the crankcase directing the crankcase pressure to charge the intake twice per power stoke. The exhaust stroke pumps the intake once and the reed valve holds the charge, the intake stroke pumps it the second time when it goes into the cylinder, so you have a 2 stroke like pumping action from under the piston and a 4 stroke firing cycle.
John Ellwood, who built this engine, says hybrid engines working on this principle began back in 1915. John got the idea to build one back in 1994 and he’s been working on the constantly evolving project ever since.
The first Ellwood Hybrid was based on a Godden engine, commonly found in speedway motorcycles, he’s also built one with a Jawa engine. The first one was converted in a pretty straightforward manner, as John describes it:
A hacksaw, drill and file were enough to slaughter the speedway engine. A bit of rubber pipe, two reed valves from an RD 350, a seal on the crankcase and a carb from a Rotax converted a relic into a Hybrid.
He has both a 500cc version which he says puts out an estimated 50 hp and a 1300cc version doing somewhere around 150 hp. The 1300 is all handcrafted and it’s fuel injected and water cooled with 4 crankcase mounted reed valves, a belt driven rotary cross head valve, an intercooler and 15:1 compression.
John has been racing the 500cc version and plans to race the 1300 in Supermono racing in the U.K. so it must run pretty well. I just think it’s an interesting combination of 2 and 4 stroke technology.
John has done a lot of work without the resources of any expensive engine building facilities. I wonder how this would run if really refined and, with the right equipment, it would be much easier to determine how much extra power this setup actually provides. Definitely different.
John adds: “…here in Sweden we’re having a flying kilometer race at the end of March, Bonneville Salt Flats style – only we do it on ice. I’ve entered the black 500 Hybrid, and will put on the laughing gas tube, to get a bit extra boost.” I checked out the ice racing website and got a chuckle, there’s a note, “Don’t bring any salt.”