For those wanting to learn more about the setup shown in the picture, there's a YouTube video and many comments here: It was posted about 5 years ago, is a pusher configuration on a trike. The engine is B&S Vanguard 627cc unit (a 38 series engine. B&S rates these as 23 HP engines at 3600 RPM. Electric and/or recoil start, 16A alternator, prices start at $1,225). Those big wrap-around tuned exhaust pipes are 38" long. The owner/builder (Kevin Armstrong, living in the UK) believes he's producing up to "about 35HP" with it, turning it above 4500 RPM. Weight is about 40-43KG (88-95 lbs --I don't know what is included in that weight--prop? exhaust?). He had put over 160 hours on it (broke a camshaft at 160 hours). Engine parts came from Performance V-Twins (North Carolina), PSRU from Ace Aviation. Modifications, per Mr Armstrong: - Raised compression by special pistons and stronger connecting rods, rather than skimming the heads. - Advanced ignition 8° - Special camshaft ( He wrote this comment: if you do go this route make sure you fit a reinforced camshaft, mine broke after 160 hours. Precision Cams do both reinforced and billet versions) - Packers to valve springs to allow higher revs - Stainless exhaust valves to withstand heat - Roller tipped higher ratio valve rocker levers, 1.5 ratio instead of 1.1 - Bigger carb off the 990cc model but with jet kit for operation at 5000' (Briggs accessory) - Open up inlet manifold to suit bigger carb butterflies - Longer tuned length exhaust tubes 29mm bore. - NGK Iridium plugs - Machined 3 kilos off the flywheel, then balanced and spin tested. Fuel consumption: On one long trip he burned 6.3 l/hr (= 1.7 GPH). Also says it " only burns 7-7.5 litres per hour (1.85 - 2 GPH) even when driven hard." If we assume a BSFC for this little engine of about .43 lbs/hp/hr, that would mean an output of up to 28 HP "if driven hard" and 23-24 HP continuous on his long trip.