Difficulty with Pull Rope Mower Start

[NJDan]

I just finished rebuilding my Honda HRX217K4HZAA mower (twice, actually). I'm having trouble with the pull start. I've been using the rope because the battery on the electric start is drained down right now. When I put the mower back together the pull start worked fine. Now I'm finding that after running the mower a bit and even the next morning cold I can't pull the cord any more. It just won't turn the motor without risk of breaking the cord. I removed the cover and turned the crankshaft bolt and it was stiff. After a few turns it feels better and I should be able to use the pull cord again. Any idea what could be happening? There's plenty of oil. Engine does run with some vibration but it is still burning off a bit of oil. I didn't run it for more than a few minutes as it was raining yesterday.

The only thing I did differently than recommended was when I attached the connecting rod to the crankshaft. I did torque it to the recommended 9 ft-lb but I did not check it with that wax paper you use to double check. I didn't bother with that because it didn't seem to be something universally used and I did torque to the recommended spec.

 

[Pauljp]

You can check if it is caused by engine compression by removing the spark plug and then trying the pull cord.

 

[sgkent]

I always spin an engine with the piston off by hand to be sure nothing binds. It can be a seal, a bearing, or piston rings that have too much friction. Do check the oil to be sure there is no gasoline in it. It can also be fuel draining into the cylinder.

 

[NJDan]

Thanks for the replies so far. A quick background and then a guess: Ran mower dry on oil last year and cratered the connecting rod. Took it apart and the cylinder looked fine. The rod journal had melted onto the crank bearing so I cleaned it up with acid per recommendations here and it looked great. Put everything back together and then the engine ran flat out like 6000 rpm. Took it apart again and found a bad governor (this is my first time working on a mower or any engine). Put back together with new governor and now RPM is right in range according to a cheap tach I bought. It does run with a vibration, though.

Problem now is the pull cord won't turn the engine after the initial run, even when cold. I can really only turn it with a wrench. The first time I put the engine back together the cord got stuck after I flooded the valves with a gas leak in the carb. I removed the spark plug overnight and the next day the pull cord worked again. This time the engine turns stiff even after sitting for awhile. I drained the oil today and it looked pretty much normal.

The only thing inside the engine that is original is the crankshaft. I replaced the piston/rings, connecting rod, governor and both crank seals, but kept the gears, which were fine. I have a neighbor's back up HRX216 from like 25 years ago and that engine can be pulled with two fingers. Here's my thought... cranking is stiff, mower vibrates when running, no gas detected in the oil. The crankshaft is the only part left from the original damage from running dry. Does this point to an ever so slightly bent shaft? Is there something else more obvious? Oh, and nothing like the magneto is rubbing against the flywheel.

 

[sgkent]

you can remove the blade, try. Remove the plug, try. Remove the top and try to turn the flywheel, If it binds then something is wrong inside. Make sure the magneto isn't hitting the flywheel, loose bolts there or something. Just keep removing things until nothing is left but the engine core. If it still doesn't spin then something is wrong. By now the rings should be broken in enough to turn the engine by hand, maybe with a little drag but not so much it takes a breaker bar.

 

[NJDan]

you can remove the blade, try. Remove the plug, try. Remove the top and try to turn the flywheel, If it binds then something is wrong inside. Make sure the magneto isn't hitting the flywheel, loose bolts there or something. Just keep removing things until nothing is left but the engine core. If it still doesn't spin then something is wrong. By now the rings should be broken in enough to turn the engine by hand, maybe with a little drag but not so much it takes a breaker bar.

I'll give that a try, thanks.