oxxy, from the crackbox universe, asks how it is that exhaust valves are
sometimes closed and why is there any pattern therein thusly:

My understanding...obviously better than yours, is that at certain
stages of the 4 stroke cycle its possible to pass air from the inlet
tract over the piston and out thru the exhaust.

not possible with a closed exhaust valve, as specified in the discussion
from
the start.

Again, how do you guarantee a closed ex valve every time?


Oz1...of the 3 twins.

I welcome you to crackerbox palace,We've been expecting you.