Several weeks ago I changed the needle & seat in the carburator.  The issue, then, was fuel overflow/spillage after starting the motor.  I would never notice fuel overflow after a flight - only at initial startup.  I am unsure if it was overflowing during flight.  A needle & seat set was pulled from the old carburator that was on the motor when I purchased it.  At that time I also lowered the fuel level that is maintained in the fuel bowl - changing two items at one time. 

After the change, upon full throttle settings (take off), I would gain about 30 to 100 feet of altitude and the motor would stumble just for a moment.  It would not loose more than a few hundred RPM but it was certainly noticeable.  At about 80% throttle it would run fine.  There was no overflow/spillage problem at startup. 

A subsequent change was to increase the fuel level in the fuel bowl.  No spillage was noticed but the starvation issue remained. 

Today I pulled the carb off of the motor and was going to put the original needle / seat back into the carb.  It was then that I compared the original needle & seat to the old needle & seat.  The "good" needle & seat set on the left, marked as a 3.3 if I recall, has a much larger hole for fuel to flow through it.  The "bad" needle & seat set on the right was marked with a 7.5 (I think).  With the larger diameter hole more fuel is capable of flowing through the assembly when it is open thus keeping the carb bowl filled with fuel for the motor's needs. 

The next step is to adjust the float level a bit lower to see if the overflow/spillage problem it eliminated.