More clearance?
Eau de Savage asked:
"For example using the 0.08—0.13 specs how bad would it be if the valves were at .2? .3?"
The analogy I used when teaching mechanics, was to think of the rocker to valve like hammer to steel. If you take a hammer, hold it very close to a piece of steel, and move the hammer, the steel moves with little trauma to the surface. If you move the hammer a distance away form the steel, and move with the same force and speed, you are more likely to deform the surface of the steel.
Valve clearances are determined to allow for almost no clearance when the valve (which is exposed to combustion heat at the large, heat absorbing end) expands/elongates.
Short answer, loose valves soon become very loose valves.
At Honda school we were taught to use two feeler gauges, or one long one folded over, on bikes with a forked rocker arm. This cancels out false readings caused by the rocker arm rocking sideways on the shaft.
Speaking of Honda school, I remember one of the guys saying that the way he adjusted valves on a twin cam 450 Honda (a bit of a PITA), was to get the bike running, loosen the clearance til the bike rattled, then tighten til the bike was quiet. Can't remember what the teacher threw at him, but it got his attention