The final drive chain was going tight/loose when the rear wheel was turned. I took the chain off and the front sprocket cover for inspection. The front sprocket was loose and the securing bolt was less than finger tight. It looked like the PO replaced the sprockets and chain. There appears to be an additional washer (the one pictured nearest the sprocket) I am guessing that this washer has actually come off the rear wheel. Without this "spacing washer" it is impossible to tighten the sprocket on the shaft enough to prevent some lateral movement. The manual refers to a 2 bolt lock plate but the sprocket couldn't accommodate this. Has anyone got any thoughts.