Answer / deependra singh parihar

Because in these engines the working cycle is completed in
1 cycle of crank shaft. so the time of cooling for the
engine is less compared to 4 strke Engines. During at the
end of compression stroke the Tempreture inside the bore
goes to 1500 - 1700 degree c. at this high temprature the
working of valves gets disturb & valves get damage because
valves are made of iron alloys.to elamanate this ports are
used.

Answer / saumya ranjan khuntia

Adding few more poimts. A valve arrangment requires some
specific arrangment and also for closenig and opening of
valve we are using spring.As all of us know that there will
be one power stroke in one revolution of the crankshaft in
case of 2-Stroke engine means actually its completing same
sequence i.e Suction,Compression,Expansionand Exhaust, but
in a quickep manner. So the process is instantaneous and
should operate more quickly. If we will use Valve, then It
might creat a problem and might affect our power
production. So in my view this is one of the important
reason for not using Valve is 2-S engines.

Answer / prem

In two stroke cycle is a simple constrction than four
stroke in two stroke cycle it can complet one cycle in
one revolution of crankshaft but in four stroke one
cycle completed by two revolution of crankshaft.

Answer / yes

yes

Answer / anjaney

4 stroke engines gives 1 power stroke in 2 revolution so
to get 1 power stroke in one revolution, two strokes need
to be completed in 180 degree so as get 1 power stroke /
revolution. this leads to development of port of 2 stroke
engine.

Answer / v.vinoth

Two Stroke Engine is gives a high power output over a wider
RPM range.

Answer / zubair

Two Stroke Engine gives high power output over a wider
RPM range.

Answer / anandan

two stroke engines have only ports. so valves are not used
here

Answer / karthick raja

in two strokes there is no need for valves since ports do work .the ports itself let the fuel in and out in 2 stroke engines whereas in 4 strokes separate valves are needed to do the work

Answer / baskaran

usually valves used in 4 stroke engine produces excess
vibration.since power output in 2 stroke is high using
valves here may lead to more vibration.hence in order to
avoid vibration ports are used here.

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