Piston window radius

[tony27]

Finally got the holes & slot put into the back of my CZ piston to Charlie Richardson's provided sketch for running a reed valve & would like to know how big to make the radius around the holes as I've never had anything to do with modifying pistons
At the moment I've basically broken the sharp edge off both the inside & outside of the holes with needle files to .5-1 mm wide, is this enough to remove to the stresses from having sharp edges


Initial work 

[Momus]

What you've done with the radius looks good to me; very similar to production Jap windows.

[tony27]

Haven't compared it to the original piston that came out of my TY250 but I will tomorrow.
Once the cylinder is back from having the exhaust port bored round to fit a new spigot I'll be looking at pulling the motor down & fitting the new stuff to it. I may buy another carb & fit the jetting kit to it so I know everything is brand new & can put the piston port stuff to 1 side together

[William Doe]

Quote "I may buy another carb & fit the jetting kit to it so I know everything is brand new & can put the piston port stuff to 1 side together"

That is good thinking Tony makes good sense