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A nice timing for standard road cams is 111 LCA 3 degrees advanced which means inlet full lift at 108 ATDC and exhaust at 114 BTDC. On that basis the OE inlet timing looks correct and the exhaust was as you say a bit odd.
Valve piston clearance on a small engine like this is usually OK at 1.5mm but of course if you never over-rev it you can go a bit tighter. You'll have no margin for further experiments with cam timing though. I wouldn't retard the inlet cam just to get more clearance though. Do it properly and machine the valve cutouts deeper.
Dave
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