Small Engines (Lawn Mowers, etc.): Honda GCV160 wont start, honda gcv160, honda mower

Question
QUESTION: Got a free Honda HR2163TDA today with a GCV160 engine. Guy gave it away because it 'just stopped starting'. This machine looks like new and is only 2 yrs. old. I checked the obvious and it looks like this guy took care of his machine. Plug looks new and spark is good. Fuel system working fine. Pulls nice and smooth. But it won't fire; even with starting fluid; just makes a sort of popping noise when I pull it. I'm guessing maybe a timing issue; but why all of a sudden, if it ran fine then just stopped? Any ideas what I should check next? Thanks for any help. Jim.

ANSWER: Start with the flywheel key.  Pull the starter and the shrods off and the retaining nut for the flywheel and see if the keyways in the crank and flywheel align.  If not, pull the flywheel, put in a new alignment key and put everything back together.  Often striking a tree root will cause the flywheel to shift and shear the key.  The ignition timing is controlled by the position of the flywheel relative to the crankshaft and the key is the reference for alignment.  Let me know if that's not the problem.  Thanks, PK.

---------- FOLLOW-UP ----------

QUESTION: Thanks so much PK. I did all that and turned out the key was still good. Gave the machine a good cleaning while I had it apart. Put it all back together and then found out I could hold my thumb over the plug hole and pull it all day. no compression. I guess the guy blew it up and didn't bother to tell me. Would a rebuild be possible and what might it involve; rings? It's too nice of a mower to scrap out. Thanks again for your help. If nothing else, this was quite educational for me. Jim.

Answer
It would depend on what has broken.  I usually replace rods and pistons just for insurance.  If the rod didn't break, then the engine should be salvageable.  Honda's are usually worth rebuilding so I would break it down and see what all needs replacement.  I imagine you can rebuild it for around $125 which would be a lot less than a new Honda mower.  Thanks, PK.