Identify typical exhaust gas constituents for either a 4 stroke or diesel engine?

Answer 1

Nitrogen (the air is 78% nitrogen, most of it passes straight through the engine).
Carbon Dioxide (product of fuel combustion)
Water vapour (product of fuel combustion)
Carbon monoxide (product of incomplete combustion)
Hydrocarbon compounds (products of incomplete combustion)
Sulphur dioxide (due to sulphur as an impurity in the fuel)
Oxides of Nitrogen (a by-product of combustion in air - due to air's 78% nitrogen content)
Soot (small particles of carbon, products of incomplete combustion)

Answer 2

Most normal diesel engines ARE 4 strokes! (The really big ones, in ships, are usually single cylinder 2 stroke 'compression ignition' - CI - engines, and those used in small-scale models are also 2 strokes/hobby shop engines).

The main constituents of the exhaust gasses, I believe, are:

Nitrogen dioxide, sulphur dioxide, carbon monoxide and heavy particulates - although what you get out of course all depends on what you put in! And if you put in, say rape-seed oil, about all you get out significantly, is carbon monoxide (which you always get when you burn anything) and a bit of water.