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That screw is NOT an adjuster! To adjust the can chain tension, all you do is looseb the locknut, with the crankshaft turned to a partcular position, and then re-tighten the locknut (the cam chain tension is automatically adjusted by a spring within the mechanism.To find the correct crankshaft position, rotate the crankshaft so the T.14 mark aligns with the timing mark on the crankcase, make sure that the number 1 cylinder valves are closed (slack in both #1 cylinder tappets) - if not rotate a full turn and check for #1 tappet slack again. Then rotate the crankshaft a further 15