Well sir, I reckon its a float valve issue, you float needle may be suspect, think of the float bowl like a toilet bowl. All the innards and principals are similar. every time you twist the throttle it has to refill. every time you flush it has to re-fill. So logic dictates to me you have an overflowing issue. There is a tab where the needle rests on it could be bent to change the flow rate, but be warned its best left for mechanics, because you have to set your float heights, I have done it to both of my cr-25o's and its a royal pain!