Using a tachometer is the only way to tell for sure if the maximum speed is correct. However the maximum speed should be the same as for an OHV Honda or chonda, and it should sound much the same as the Honda, and somewhat quieter than the chonda (chonda mufflers don't seem to work as well as Honda ones, at least to me).
It sounds as if the decompressor probably wasn't working with the huge exhaust valve clearance you had, and now that you've corrected the fault it is working properly. The starter will last longer on part compression.
The choke should just barely close fully, when the speed control is at maximum/choke. Try backing off the speed lever a little, and see if the choke opens with the smallest movement of the lever. If it doesn't, an adjustment is needed. I'm used to the OHV engines, which have a screw-stop on the governor plate to control how far the lever can move. I screw it in until the choke doesn't quite close, then back it off until it just barely closes. I don't recall what equivalent adjustment the OHC engines have. If the speed control can move too far, it may close the choke then move further by distorting the linkage. Movement of the speed control lever stretches the governor spring further, increasing the maximum speed, so you have to set up the linkage so the choke just barely closes when the speed control lever is pushed as far as possible.
