B&S 12.5 crafstman hard to start?

The engine will rotate about +/-1/2 turn, then stop. If the flywheel is manually rotated either way past the compression/exhaust cycle, it will rotate another +/-1/2. If you're lucky, with the help of a car battery and jumper cables, you may be able to get it to rotate 1 or 2 revolutions and possibly start. When running, it goes fine. Motor will turn freely with no plug. I have already put in a new battery and checked the spacing between the mag. and flywheel The tractor is only 4 years old with little use.