Just be sure about somthing,are you sure this is a 30cc.The numbers your stating are what my echo 22ccs run with a 15x8.Also,on page 2 you said something about a clicking noise when the piston comes up,this might be a cracked or broken ring hitting the intake or exhaust port.One other thing you mentioned was crankshaft play,was this end play or was it play at TDC when you rock the hub or flywheel back and forth at TDC.If you have more than 1/4 inch of play,rocking motion at TDC,and the piston isnt moving,then you may have bad rod bearings top or bottom.End play on a crankshaft is fine and most all engines have a little most of the time from the roller bearings.I bought a new tach and ill put a CF 18x8 on my 28cc stihl and see what it does.