What is the proper RPM settings for small engines?

Answer 1

It depends largely on just how small an engine you are talking about, and how many cylinders it has. A car with 4cylinders for example may idle at around 1,000RpM, whereas a motorbike with 3 should idle at closer to 1,300RpM.

You can generally tell if an engine is idling at the correct speed by the sound of it. If it sounds like it's going to fast, it probably is. If it stutters or dies, chances are it's idling too slowly.

Very small engines, such as those found on lawn mowers or chainsaws, etc are a bit trickier to adjust, as their operating temperature is attained faster due to their size. Generally these engines should idle slightly faster than is necessary to keep them running.

It may take several days, even weeks of constant adjustment & testing to any engine before it will idle at its correct speed. If you have a manual for a particular engine it should tell you exaclty how to set the adjustable parts (needle valve clip, spark plug gap, timing, points gap, main and sub-jets, mixer screw, etc). It helps if all these are adjusted correctly to begin with, as re-adjusting one thing may make something else perform worse.