I tell my readers that engines need not cost $300 or even $400 but $20. So the search is constantly on for a cheap engine.
I received this email the other day which basically sums up a typical engine problem. You go out see an engine and wonder if buying it was such a good idea.
“I just purchased a 20 dollar fairly new 5hp lawnmower engine. I’ve got it home, and I can’t seem to start it. There is a lot of tension, and I can’t seem to pull the string all the way. Am I doing something wrong?”
Obviously, engines are supposed to spin, but you get these once in awhile situations where an engine does not spin. First of all it is important to understand why an engine spins, and then secondly, what would cause it not to spin.
9 times out of 10 and engine will not spin because something external is wrong with the engine. The other 1 out of 10 problems are internal. And to put it into perspective most engines can be fixed so that they will spin again, using little or no money.
So to start it is important to understand the externals of and the internals of an engine…
The outside of the engine is really a shell with a shaft sticking out one side, and a flywheel on the other side. Then attached to this box is a fuel system (carberator) and an exhaust pipe. As you have learned in other articles, the magneto is attached to the flywheel side of the engine, and grabs magnetic pulses from the flywheel to make sparks for the spark plug. junkyards near me
To cool the engine down, there is a glorified fan on the engine and it is incorporated into the flywheel. The fan is covered with a shroud that routes the air around the engine blows the heat off the engine.
To cap it all off, typically on the flywheel shroud housing is a starter pulley system.
The internals of the engine to the casual observer looks like spinning gears, and oscillating parts. But you and I know that the main parts are the crank shaft, the cam shaft, the valve tappets and valves, the connecting rod, and the piston.
(I am assuming an understanding of the Otto Cycle or the Two Cycle engines, if not please read articles on these topics)
The main thing to understand about the engine internals is:
– the crankshaft must spin freely
– the piston must slide up and down freely
– the connecting rod should articulate around the crank journal freely
– the valves must move up and down without and resistance.
To keep an engine from spinning, something has to interfere. Interfere means, block, or get in the way.
For example a rusted bearing does not spin because the balls are now not spherical but bumpy with rust. A bumpy bearing will get jammed on the bumps and come and we say “ginding to a halt.”
Rust also has a nasty habit of actually filling in gaps and making things solid. A shaft in a bushing for example will expand with rust and become jammed in the bushing