I have a 2003 STX-DI 1100. Machine will crank and almost start but backfire hard. Suspect timing issue or fuel issue. Checked for spark with gap tester-OK. Checked for fuel injection-seems OK. Removed crank sensor to check timing marks. TDC 1 and 2 timing marks appear in window, TDC 3 timing marks not in window. Because timing marks are only off in 1 cylinder, suspect twisted crank other than sheared key. Kind of an old school wrench, new to this forum. Any suggestions would be greatly appreciated.