MOPED ARMY

To measure the ports you need to just compare width and the timing, the timing will give you the mean effective area which you need to compare the output of the engine. ALso it is needed for port timing so you can get a proper exhaust expansion chamber happening if you are going for performance.

Stock _fast cylinder_ on a 1970 50V intake opens 132 btdc, transfer 130 atdc, exhaust 113 atdc. because the timing on a two stroke is symmetrical you can figure the duration of the event into intake 96 degrees, transfer 130 degrees exhaust 134 degrees.

No Steve, I just research lots and try to do it right the first time, not everything works perfect but then that wuld just be boring.

This has been said over and over.

The letters on the cylinder have nothing to do with the porting. They're only for factory matching of pistons to cylinders. The bore was off by thousandths of mm from the factory and pistons were matched to cylinders by a lettering system.

Also, almost all pistons will work with all cylinders, so disregard the lettering all together and just look at the ports.

Are you sure that 50 didn't tell you this stuff?

To convert from port height to diration in degrees you can use this formula for exhaust and transfer

Duration = (180 - COS ((T^2 + R^2 - L^2) / 2 R T)) 2

R = stroke / 2 in mm

L = conrod length in mm

C = Deck clearance in mm

E = Distance from port top to deck

because the intake is below the piston top for intake the formula is

Duration = (COS ((P^2 + R^2 - L^2) / 2 P R)) 2

P = R + L + H + C - F

R = stroke / 2 in mm

L = conrod length in mm

C = Deck clearance in mm

H = Distance from port top to deck

F = Port floor depth [deck to bottom of port]

Arran, me n 50 do share some secrets!

damn. I don't like math, but I will work this out.

my eyeball is the best calculator around, god i hate math.

thx for the info warisesi.

remember when looking to amke ur bike faster that power is in the points just as much as its in the ports if not more so