Using outboard boat engines
During 1973 the final Konig 500 version produced 85hp at 9800rpm.the engines were developed into 350cc, 500cc, 680cc (90hp) and later 750cc versions to suit the various hydroplane classes, with many of the larger engines later going into sidecars. When fitted to an outboard the Konig engines had the crankshaft vertical in order to drive the prop shaft, with the exhausts on one side and the Konig-produced special carburettors on the other. The lightweight 55kg (with gearbox) ‘boxer’ type motor is fitted into the frame in a north-south direction with two cylinders facing forward and the horizontally opposed pair facing rearward. Each side shares the same crankcase and each side (left then right hand side) fires at the same time (big bang style), with a 180° firing interval between the left and right pairs. Each side shares the same carburettor and crankcase charge, meaning just one horizontally mounted double-barrelled down-draft carburettor feeds the single disc valve controlled powerplant. The Konig 500 was revamped during 1973 to run larger 42mm (up from 38mm Solex units) Tillotson pumper jet carburettors that also allowed better clearance for the left-hand exhaust pipe, further away from the heat of the unsilenced expansion chambers. The four single ring forged Mahle pistons have a hole in the bottom skirt to allow a third Mz-style inlet port to enhance the fuel/air charge. An electronic Krober tachometer was installed to monitor revs, while a high quality West German Hoeckle single crankshaft was used with caged roller big end bearings and needle roller small end bearings. Unusual for a four-cylinder two-stroke, the Konig engine has only two exhaust pipes! A two into one ‘Y’ branch was used on the outboard engine. However, there was no space for four pipes on the bike, so the ‘Y’ branch pipe system was adopted on the race machine. When one piston is up, the opposing piston is down, so when one fires the opposite side is blocked off by the piston. It worked very well, as the 85hp Konig 500 was often faster than anything else on the track, including the MV Agustas. One of the biggest issues to overcome was keeping the engine at a lower than normal 60°C – its optimum working temperature due to its recirculated total-loss cold water boat design.this was achieved using a Berlin-made but super heavy double-core five-litre brass radiator with a cooling finned magnesium sump-like reservoir bolted underneath the engine. A water pump operated by a pair of extremely tiny but usually reliable rubber belts runs off the crankshaft. Overheating problems were mostly sorted in mid-1972 when Newcombe introduced ducted air from the fairing.