Small Engines (Lawn Mowers, etc.): Hard to pull 13 hp Honda engine, hp honda engine, woodruff key

Question
Michael,
I pulled the flywheel and the woodruff key looks like new and was in place.  With the flywheel off I tried to turn the engine over and have the same difficulty once it hits the compression stroke, it gets very hard to turn.  Does this mean the engine timing is off somehow ?  Any suggestions on how to check/fix the timing?  Or should I open up the block and see if all the dots are lined up ?  (I don't know how they are supposed to be lined up anyway if I open it up.)  I would like to avoid doing that but I also want the engine to run.
I appreciate your help.
Thanks,
Scott.

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Followup To
Question -
Michael,
This motor is on a Keys walk behind commercial mower.
However, currently nothing is hooked to the motor it is just bolted to the deck.  
The recoil doesn't really pull back as much as it is just hard to pull over what seems to be the compression stroke.  The flywheel does seem to turn a little in the opposite direction after the pull as a kick back.  If I don't start pulling when it's hardest it will yank out of my hand once it hits the compression stroke and just want to stop my pull.
Thanks,
Scott.

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Followup To
Question -
I have a 13 hp honda engine which is very difficult to pull the starter cord.  When I remove the spark plug it is very easy to pull the starter cord but once the plug is replaced it takes quite a bit of effort to pull the cord to turn the engine over.  The engine does turn over and has started a few times but only runs for a few seconds at very low RPMs then stalls before I get a chance to give it gas.  I have cleaned the head, the combustion chamber and carburetor.  What else can I do to make it easier to pull the starter cord to get this engine running good.
Thanks for any suggestions you can give me.
Scott.
Answer -
Hi Scott,

Is the engine on a push mower?  Does the recoil seem to want to pull back out of your hand at all?

Michael
Answer -
Hi Scott,

As I suspected, it seems like the flywheel key is sheared.  This is common when either an object is hit with a blade or if the flywheel is loose.  On an application where the blades are isolated by a belt, the flywheel is protected but with a direct drive from the engine to the blade/s, any impact is transmitted to the flywheel.  The only other possibility is that the ignition timing has gotten advanced.  With modern solid state ignition this rarely happens.  So, I would pull the flywheel and take a look.

Let me know how you make out.
Michael  

Answer
Hi Scott,

Valve timing shouldn't be off at the gears, (which have dots or marks to line them up,) unless you think the engine was apart before the problem started.
The only thing left is the ignition timing.  If there are points, you can adjust the timing there but if electronic ignition, the timing usually stays correct unless the unit is faulty.  I don't know what else to try.

Please keep me posted,
Michael