Do you need an overhaul?

The following are indications that at least a partial overhaul may be needed:

• Mechanical damage - broken, damaged, or bent parts resulting in inability to start or even turn the crankshaft for starting or excessive vibration while running. In most cases, this will be obvious - the mower died very suddenly - possibly with a loud clunk or p-ting and now the crankshaft hits something really really solid inside when attempting to pull the starter.

• Low compression - this is due to wear or abuse (lack of oil) of parts like the rings or valves or due to a blown head gasket. Perform the compression test described in the section: Compression testing. Symptoms would be difficulty in starting and unusually little resistance when pulling the starter cord, and perhaps, loss of power once you get it started. If rings are bad, there may be excessive oil consumption and blue exhaust smoke. If only the valves are involved, only the cylinder head may need to be removed.

• Excessive oil leaks - a failure of the oil seals (the lower one on mowers at the PTO/blade end, most likely) will result in oil dripping or pouring from under the mower deck. The blade will be coated with oil and there will be a puddle where the mower is stored. Of course, if this is severe enough or neglected, you may end up with much more serious problems when the internal parts fail due to lack of lubrication. Replacing an oil seal is not difficult. The old seal is removed by piercing its thin metal shell with an awl or ice pick and carefully prying it out. Take extreme care not to scratch or dent the mounting surface or crankshaft. This may be possible without extensive disassembly. The new one is then pressed on. In fact, installing the new seal is best done with the crankshaft in place as there will be less likelihood of damage to the new seal and it can then be driven in straight. There is a special tool for this but a piece of pipe that just fits over the crankshaft cut off square will work just as well. Remove any burrs on the crankshaft to prevent damage to the new seal and take care that any rubber lip on the seal does not get folded over.

• Excessive noise - knocking, banging - while an engine powered piece of machinery is not exactly quiet, there should not be unusual or excessive mechanical noises. Such noise can be an indication of an excessively worn engine or of some part that is about to fail. Should you strip the engine based on this? I cannot say - it is a judgement call. It something about the sound suddenly changed, then investigating the cause is certainly warranted.

In some cases, multiple problems may be present and/or there may just be excessive wear of parts like the cylinder, rings, and piston. Under these circumstances, the cylinder may need to be rebored to accept a replacement oversize piston and ring set. The cost of the parts and labor (you really don't want to rebore a cylinder) will likely be more than you want to spend. This is when a new engine or mower is the best option.