e10eafa103fb                                                                                                                                                           The KNUCKLEHEAD was built from 1936-1947.This was not Harley Davidsons first overhead valve engine(the first one was the 21 cid. peashooter). It was originally called the 61cc OHV.KNUCKLEHEADS had the first recirculating lubrication system and oil pressure gauge.This was the start of the trademark harley dash with gauges mounted on the tank.Also this when harley started using independent oil tanks.Finally this bikes became known as knuckleheads due to the shape of the rocker box covers.In 1941 harley introduced a 74cc version.