So I got a china girl and I "upgraded"from 47mm piston to a 49mm "big bore".

[Over did it again]

When the Piston travels all the way down to bottom dead center the intake is not completely closed off there is a little bit of Gap at the bottom. Is that okay or is it supposed to completely seal off

 

[Greg58]

A picture would help, are you saying the piston skirt or window never is fully closed? If you are running reed valves it won't be a problem.