If the valve timing is correct and there are no damaged engine parts (or weak/faulty valve springs) that should not happen, yet however if the engine is "over-revved" the valves could "float" which is not normal operation. (If the engine is an interference engine there may possibly be engine damage.)
That is normal and it is called valve overlap.
overlap
In a four-stroke engine its called the compression stroke
It is called the compression stroke.
'a 4 stroke engine cycle' is usually what it is called...
You can use four stroke oil for a (very) limited period in a two stroke engine in an emergency. However it is not formulated for two stroke engines and is not recommended.
Yes. A 2 cycle engine is also called a 2 stroke engine.
There is a short time between the exhaust and intake stroke where all the valves are slightly open at the same time. This period of time is called valve overlap. This is because the intake valves are just starting to open as the exhaust valves are just finishing closing. This is done so flow through the engine can be maintained at engine operating speeds.
Explain the advantages of four-stroke engine over two-stroke engine
Oversquare
Four-stroke engines have a spout where you add oil to the engine. On two-stroke engines, oil has to be added to the fuel. (Four-stroke and two-stroke are also called four-cycle and two-cycle, respectively).
two stroke
Why the fuel consumption is less in 4 stroke engine as compared to 2 stroke engine