Scavenging
'a 4 stroke engine cycle' is usually what it is called...
stroke
You're talking about an engine compression brake, commonly referred to as a Jake Brake.
Usually no.
The most efficient to date is a 2-stroke design. it is a turbo desiel 2-stroke. but normally a 4-stroke is usually the more efficient of the two engine types.
Depending on the type of 250cc engine, two-stroke or four-stroke, and the state of tune of the engine you can expect anywhere between 20hp for a nice relaxed trail bike to over 40 hp from a fire breathing two-stroke motocrosser.
Usually none at all.
Explain the advantages of four-stroke engine over two-stroke engine
A hemorrhagic stroke relates to your brain. Strokes can occur in large or vast amounts (small usually referred to mini stroke). Strokes all take place in the brain. Some people usually think strokes are heart related.
A 4 stroke engine is also referred to as a four cycle refers to the internal combustion whereby the piston completes 4 separate strokes with a single thermodynamic cycle.
two stroke
Usually none at all.