Not sure about other 2-strokes, but I  from what I remember, the
little 250cc one in my dirt bike has no "valves". Just a device to let
the proper amount of airflow through the combustion chamber so most of
the exhaust is pushed out.

I haven't taken it apart in ages though...

Sudhir

On 8/20/07, Pensioner <al_knoll@pacbell.net> wrote:
> Lift and Duration are the two parameters of interest in cam design along
> with the ramp geometry.
>
> Lift is how far the cam pushes the valve open.  Measured in inches.
>
> Duration is how long the cam keeps the valve open.  Measured in degrees.
>
> Overlap is the degree (Degrees/360) of total rotation where both the intake
> and the exhaust valves are open at the same time.
>
> The ramp geometry determines the acceleration of the valve and valve train
> as it is pushed up by the cam lobe.  This attribute helps to determine the
> rpm at which valve 'float' occurs.  When the valve cannot follow the
> oscillation of the cam lobe it is said to 'float'
>
> Why don't 2 stroke engines have valve float? (NVC).
>
> Al (some cats are two stroke)
>