Thanks for the info guys. Bill, I could never quite understand about the hot & cold clearances in our model engines, but what you say makes sense. I spent too many years with my first love, car racing and adjusting the valves on solid lifter cams, I couldn't see the forest for the trees.

As far as the clearance goes on my YS .63 I was originally able to pass both the 0.1 & 0.04 guages TOGETHER under the rocker arm, so by setting it to 0.04 should make the difference and cure my problem. Again I couldn't see the forest for the trees, I was bound and determined that the valve lash should be OK after only 5 flights, another lesson learned. [&o][&o][&o]