any one out there know how to fix lawn mowers?
what are the most common problems of a lawn mower not starting? how much compression is there? can you feel the compression if you plug the hole with your finger and crank the engine? how can you test the coil?
In my experience, the most common hard starting problem is stale fuel left in the fuel tank over the "off season."
As the fuel evaporates it tends to clog the small galleries [passages] inside the carb and creates fuel "starvation" when trying to start or run. IF this is the problem it usually requires dissembly and overhaul of the carb.
IF you're lucky you may correct it by pouring all the stale fuel out of the tank, and refilling with fresh fuel to which you've added some Carburetor Cleaner or Fuel Injection and Fuel System Cleaner, both of which are available at any auto parts supply store.
As for compression, you "feel" it quite well when trying to crank the engine while pulling the starter rope handle. Compression causes the resistance you feel. But yes, if the engine has good compression, then during that cranking test the compression will be felt with your finger, and PROBABLY will "blow" air past your finger. You generally cannot "hold back" the compression of any engine.
Even with an electric start engine you can sense the difference by how labored the cranking is with the plug in compared to when the plug has been removed. There will be a difference in the SOUND, and also in the speed at which the engine turns over during cranking.
Most ordinary mower engines do not have a coil, as the spark is created in the Magneto. To test for spark, remove the spark plug, attach the spark plug wire back to the plug, and hold the plug threads tightly against the engine metal to ground it. To reduce the chance of getting shocked, hold the plug with a well insulated pair of pliers, AND WITH a leather glove on your hand.
Then while the plug is grounded, crank the engine and look for intermittent sparking in the "gap" in the plug. Depending on circumstances, is MUCH easier to have a second person helping during the plug spark test.
To tell if there is a lack of compression problem, turn the engine over by hand with the spark plug IN. Then, remove the plug and crank the engine again. Without the plug installed, there will BE NO COMPRESSION. By comparing the difference in the two tests you can tell if there is a problem.
IF it is just as easy to crank with the plug IN as when the plug is out, then there is a problem of lack of compression. I doubt you have that as unless an engine is totally "worn out," there is always compression.
