Here's an unrestored Yamaha YL1 from 1967. This
particular example belongs to Steve Cooper. The piston ported 100ss twin was developed from the Japanese market
only AT90. The bike is an American market model that required a very thourough decoke along with new set of pistons
and rings due to what looked liked a cold seizure early in its life. The YL1 is a rare mini-beast these days and
normally attracts a crowd when it's parked up. The silencers do a reasonable job aroud town at lower revs but as
soon as the throttle is wound open the slash cut pipes start to scream and Steve descibes the sound as being like a
pair of demented chainsaws!