why do some engines have reed boxes (REEDS) and some dont.such as my poulan 46 ccis open port to the carb. thanks scott

Just different designs. What you have is a piston ported engine, which only means that the piston going up and down opens and closes the intake port.

A reed valve engine has the intake port somewhere in the crankcase area usually, and has a reed valve to control the opening and closing of the port. Whenever there is suction, it opens, when there isn't, it closes.

There are pros and cons for both. A reed valve engine often makes a more tractable engine, with good low speed torque. At higher rpms, the reed valve and it's assembly become a restriction to airflow and can hurt top end power.

Just the basics there....

AV8TOR

thanks for the reply av8tr much appreciated

I believe because it's less expensive to produce a piston port engine and piston port engines produce more power at higher R.P.M. without the retrictive reeds and reed cage. Reed induction engines may be more efficient and tractable throughout the RPM range though.

Bill