starts but don't think it's compressing
 

does this mean the connecting rod is snapped? honda 2002 400ex. sorry if i sound like a complete idiot but i'm new to this. anything else it could be? thanks for the help

if not getting compression could be many things (piston has a hole, rings are bad, gasket, weak spark etc) if its the connecting rod it wont start at all and when you turn it over there should be a loud knocking sound

It prolly has a worn top end it wouldn't run at all with a hole in the piston or a broke rod if it starts but lacks power or smokess bad it is a worn top end if it is nosiey then. Timing chain might have jumped time it is a couple things 400 an 300 ex are know for but they run for ever

thanks for the info.

No problem let us know what u find out

If it has no compression, it wouldn't even start.

depents on the size I have seen 2 cycle that would start but had little compression and had a pinhole in the piston where someone put straight gas instead of mixing it didnt run it too long and burned a pinhole in the piston