I picked up a John Deere 14SB in hope of repairing it and at worst parting it out. It didn't have any compression when I pulled the spark plug at the sellers house and negotiated accordingly. When I got home I took the air cleaner off, pulled the cord and noticed air was popping out of the carb/intake. This made me thing something was wrong with the intake valve, possibly stuck open. So I pulled the valve cover off and found a busted valve spring retainer and a bent pushrod. I pulled the head off to find the intake valve also bent, so it has had a collision with the piston, but no damage on the piston. Now I'm trying to figure out what cause this and if I replace these parts will it happen again. The intake valve lifter was stuck up, but a very light tap loosened it and both intake/exhaust lifters seem to be moving the same. Seems to me if the valve spring retainer broke how did the pushrod get bent? I'm thinking maybe the intake lifter got stuck causing the piston to hit the valve and bend the pushrod, but the light amount of force I used to get the lifter loose seems it would have popped loose when the piston hit the valve. Any ideas what went wrong? Can I get these parts somewhere cheaper than the JD dealer? Would hate to throw parts at it and the same thing happen again because of something I missed. I'm new to this mower, but have rebuilt some other things. This is a 4.5hp Kawasaki. Any input is greatly appreciated.