While for certain repairs it is quite possible to work on the engine while still mounted on the mower or other yard equipment, it will almost always be much more convenient to disconnect and remove the entire engine to the convenience of your workbench. There are generally only a handful of actual connections. A typical small engine is remarkably light and compact once stripped of the mower deck!
- Disconnect and secure the spark plug wire.
- Drain the gasoline or remove the fuel tank and store in a safe place.
- Drain the oil from the crankcase/oil sump. While this is not essential for all overhaul operations, it will eliminate any risk of oil pouring out or going where it should not when you turn the engine over or on its side. In addition, this further reduces the risk of explosive fumes which might result if excessive gasoline has contaminated the oil. Finally, now is a good time for an oil change! Refer to the section: An oil change isn't really a big deal. (However, you won't be refilling until later.) Don't reuse the old oil even if you recently changed it and dispose of it in an environmentally friendly manner.
- Brush or vacuum off the exterior of the engine above and below the deck and then wipe it down with an old rag to remove decayed leaves, grass clipping, dirt, oily grime, dead (or live) rodents, whatever. The cleaner it is when you actually start work, the better off you will be and there will be less chance of contaminating the interior.
- Detach (and label if there is any doubt about how they are connected) any throttle or dead-man control cables.
- Remove the blade (or anything else driven by the crankshaft). See the section: Non-violent blade removal. Don't lose the locking key if it is separate!
- Remove any auxiliary drive (self propelled) or power take off. This may be a belt or chain above or below deck.
- Disconnect any electric start wiring from the mower.
- Check for and remove anything else that would prevent the engine from being detached from the equipment.