Unlike the Detroit-era Henderson four cylinders with their inlet-over-exhaust valve arrangement, the Chicago-era bikes were side-valve “flatheads”. The engineering of combustion chambers was evolving rapidly in the 1920s and particular accolades are given to Harry Ricardo, a British engineer. He developed a combustion chamber design that minimized pinging (aka, knocking) with improved fuel turbulence and combustion, smoother operation and greater horsepower than previous designs. Numerous motorcycle, automobile and airplane companies licensed the Ricardo design including Schwinn for the Henderson Deluxe. Finding some cylinders with Ricardo chambers in good condition was accomplished my our engine builder, Mark Hill of 4th Coast Fours.
The assembly of our ‘28 engine incorporated some enhancements used to overcome certain design weaknesses. Most importantly, we need to assure reliable delivery of clean oil at adequate pressure to the crankshaft, pistons, rods and transmission. The oil pump was modified to provide additional lines to an external, spin-on filter cartridge and to the main shaft of the 3-speed transmission. That main shaft was line drilled with oil outlets into the shaft bearings. Here is a picture of the rear of the engine showing the shaft and gears:
The crankshaft is supported by three main bearings but this engine got “special treatment” as shown here with Carrillo rods and custom bearing shells:
Next up, frame repairs and preparation.