What is the difference between a 4 and 2 stroke

[cdsonsini]

Ok this just shows my ignorance... Can someone describe the difference between a 2 and 4 stroke motor to me?

 

[noelm]

Re: What is the difference between a 4 and 2 stroke

be much easier to o a google and find it, but here is the condensed version (very condensed) a 2 stroke does not have a camshaft and an oil sump, oil is mixed with the fuel for lubrication, as the piston decends it creates a low pressure and uncovers a hole (port) in the cylinder, this is connected to the carby system and draws fresh fuel and oil mix into the crankcase which is transfered via air pressure from the decending piston to another port into the top of the head ready for ignition, the piston moves up and the spark ignites the fuel load, driving the piston back down to start the cycle all over again, making 1 power stroke every revolution, or 2 STROKES of the piston, 4 stroke system to follow

 

[noelm]

Re: What is the difference between a 4 and 2 stroke

a 4 stroke has an oil sump and oil with a pressure pump to provide lubrication, as the piston decends in the cylinder, a valve in the head opens, which is connected to the carby, the low pressure from the piston draws fuel from the carby, through the open valve into the combustion chamber, the piston starts to move up the cylinder and compresses the fuel/air mix, a spark plg fires the mix and sends the piston back down again, as it comes back up, an exhaust valve opens and the spent gas is forced out into the muffler, the piston continues on its down stroke and starts the whole proces again, completing 4 STROKES of the piston.

 

[noelm]

Re: What is the difference between a 4 and 2 stroke

OK now for the advantages of both, a 2 stroke is very simple, a single cylinder engine requires only 3 moving parets, fuel/oil costs make it usually confined to smaller HP sizes, it has a smokey exhaust and is difficult to muffle, a 4 stroke is mechanically complex, with lots of moving parts, is heavier but it runs clean, uses next to no oil, and will idle smooth even without load, now before veryone throws rocks at me, this does not take into account modern oil injected or fuel injected outboards and so on.

 

[robert graham]

Re: What is the difference between a 4 and 2 stroke

If you can Google up a video, it would be much easier to understand, this being a classic case of "a picture is worth a thousand words". Good Luck!