Small Engines (Lawn Mowers, etc.): water meter, putt putts, metal keys

Question
I hit the #@%$^%&^ water meter with my MTD. Do I straighten the blade in a press and pound the crank straight, (I'm a tool and die maker" I can get it pretty straight.
Or do I sell the blade at a garage sale?

Answer
Paul
The assumption is that the engine started and ran normally prior to the incident.

If the blade struck a solid object while the engine was set on 'high', more severe damage is possible as even with soft metal keys locking the blade and flywheel to the crankshaft, the inertia of the rotating blade is acting sideways against the crankshaft in addition to suddenly stopping its rotation. This can result in a bent crankshaft. The end of the crankshaft with the blade adapter could be bent without affecting the bearings or internal parts. This would need to be tested for as well. Not that such an occurrence is that much better - the crankshaft would still have to be replaced but at least the bearings in the crankcase will not be damaged.

If the starter will not turn the crankshaft (assuming you remembered in your haste to engage the safety bar) - it is seized or will only rotate part of a revolution before hitting against something solid inside - then you probably have serious internal damage that will require a complete strip down and replacement of some (expensive) parts. If it turns but much more tightly than you recall (assuming you do have the safety bar engaged!) then the crankshaft may be bent - again very expensive. Repair may not be worth it. Fixing  or trying to straighten one out is not that good of a idea.

However, in most cases, what has happened is that either or both of the blade lock key and/or flywheel key have sheared to protect the crankshaft from serious (and terminal) damage.

If the blade lock key broke, the blade will no longer turn rigidly with the crankshaft and provide the inertia required by many small engines with undersized flywheels. In this case, the engine may try to start but die out with a few "putt-putts" or even kick back on the starter cord. (As a side note, attempting to use a lawn mower engine as a replacement on a piece of equipment that doesn't have something to substitute for the blade's inertia may not work for this reason.)

If the flywheel key broke, the ignition timing will likely be totally wrong and the result may be no ignition, backfiring, kickback, or weak or total loss of power.

Thanks