MY 1947 8N HAS ALWAYS STARTED UP NEARLY ON CONTACT WITH THE STARTER SWITCH. YESTERDAY I STRTED IT DROVE ABOUT 100 FEET, TURNED IT OFF TO GREASE MY MOWER AND NOW THE TRACTOR WILL NOT START. THERE IS SPARK AT THE PLUGS, BUT THE ENGINE DOES NOT FIRE IT JUST TURNS OVER EASILY. THE PLUGS WERE DRY...