QuestionHi,
A friend wants to give me his lawnmower that he snapped the blade off of when hitting a rock. I am fairly handy, but I can't tell if this is a part I can replace with the simple tools I have at home, or if this is a major tear down and repair. Any thoughts you could share would be most helpful.
Many thanks.
AnswerHi Rick,
If the crankshaft is broken off, you would need to replace it. That would require disassembly of the engine. If the blade ONLY, is damaged, you would need to remove the flywheel and replace the flywheel key that most likely sheared off, upon impact. Below is my general proceedure.
Let me know how you make out.
Michael
If it quit right after striking an object, I could almost guarantee that the flywheel key is sheared. The timing would then be off. The flywheel is located under the recoil/cooling shroud. Its' bore is tapered and mates with the tapered crankshaft. The keyway in the flywheel and shaft keeps it from spinning on the shaft. A nut secures it. Use an impact wrench on the nut or a strap on the flywheel. Don't put force on the cooling fins or they
will break. The recommended way to remove a flywheel is to use a puller. An alternative, is to tap on the crankshaft top, with a brass hammer or use a punch
tip on an air hammer. The flywheel will need to be held up and supported or upward pressure applied with 2 large prybars. (A 2 person job.) Care is needed so the flywheel
doesn't crack or bend. Also be careful to not mushroom over the crankshaft top. Replace the key. Install the flywheel after cleaning the tapers and re-tighten the nut to 65 ft/lbs.
There is also the possibility of a bent or twisted crankshaft depending on the severity of the impact but usually the key just shears.
