Date:         Mon, 20 Aug 2007 09:10:32 -0700
Reply-To:     Bob Donalds <donalds1@VERIZON.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Bob Donalds <donalds1@VERIZON.NET>
Subject:      Re: Cam timing
Comments: To: Sudhir Desai <sudhir.desai@GMAIL.COM>
Content-type: text/plain; format=flowed; charset=iso-8859-1; reply-type=original

Two strokes dont have valves to float

Bob
----- Original Message -----
From: "Sudhir Desai" <sudhir.desai@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, August 19, 2007 11:59 PM
Subject: Re: Cam timing


> 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)
>>