Speedfight compression (i thinks)?

Well i was going along after leaving the bike sitting about a month and was running fine all day no probz then i hit a small bump and it bogged right down and had no power i managed to get it home and soon as i turned it off it sound like it had no compression at all. all gaskets are fine and it didnt go bang or sound as if anything broke ERGHH
Help pleasse

Ps. Barrel and piston new but been running fine for about 400 kilometers