This may or may not be an issue you face that I just resolved on a 92 Mountain Cat EXT 550. Although mine is carbed. The fuel pump uses Crank Case Pulses in order to draw fuel. It had a front crank seal leak which would not allow it to develop the pulse on the #1 Cylinder. Started poorly, ran poorly, would not rev up, was difficult to keep running in general. A compression and cylinder leak down test was inconclusive. By removing the intake and blocking the ports I was able to use low psi air pressure to pressurize the crank case and then listen for excaping air. Replaced the front seal, sync'd the carbs and runs like a Champ once more...........
