I operated the engine for about 15 minutes at full power without a problem then it lost power at high speed and sounded like it was cycling up and down (not missing more like a vrooom vrooom sound) at a lower RPM level. After <br />throttling down to half speed the engine smoothed out and ran fine but only at half speed. I tried to increase speed and it cycled up and down again until I adjusted to half throttled.<br />I changed out the spark plugs and put in a new coil but after 10-15 minutes at high speed it did the same thing again, it almost sound like its running on one cyl at high speed until I<br />back it down to half throttle. Any thoughts on what the problem might be?
