Yamaha 500 singles do not have plain bearings except the small end of the connecting rod, and sliding valve lifters, same as a Vincent, everything else is ball or roller bearings, built up crankshaft, one piece connecting rod, dry sump, Yamaha oil capacity is less than Vincent, 2.4 liter, oil pressure the same or less than the comet, typical for engines with rolling element bearings, recommended lubricant 20W50, the major lubrication difference between Comet and Yamaha is that Yamaha's engine oil also lubricates the transmission and primary drive, so even more opportunity for the oil to get into trouble .