Small Engines (Lawn Mowers, etc.): Lawnmower broken again, speed lever, high grass

Question
I have an old Murray lawn Mower (maybe about 5 years or more) with the big wheels in the back and it has a variable speed lever on the frame that I like. I recently had it repaired, cost me close to $85 to repair and the problem was the carburator was filled with bad gas and needed to be cleaned. After taking it from the shop it started promptly, but after using it for a second time, going through some high grass( about 5-7 inches high) it broke again with a big Kaplunk! Should I spend more money on it again to repair?(it has a brand new blade also).. When I tried to pull the chord on the side to start it, it was very hard to pull, like the engine was seized.. I liked this mower very much for the variable speed lever on it. The newer ones I am looking at Sears or Home Depot do not have the lever for variable speed. I am disappointed in seeing this. What do you recommend?   Michael

Answer
The first item to check is the crankshaft.  Remove the sparkplug and see if the sting pulls easy.  If so, have a helper raise the mower.  We usually have the helper stand on the mower handle with the shut-off lever squeezed.  Have the helper pull the string while you ovserve the blade.  If it appears to wobble, then the crank is bent and the mower is not worth fixing.  

If the crank is fine but the string is still difficult to pull with the spark plug remove then the shut-off cable may be stretched causing the flwheel brake not to fully release.

Check the crankshaft first and let me know what you find.
Eric