Jucks

Hi everyone, i have been having running problems with my S2, it runs on cold start then cuts out.. After trying everything under the sun.. checking for air leaks etc... i noticed that somehow there is fuel leaking into the metering head, (as in, underneath the flap under the air filter) obviously this isnt supposed to happen, so i took my it apart, and cleaned it / wd40'd it all, but i noticed that the piston is jammed in (Is this normal, when theres no pressure to push it out, or is it jammed?), if so this must be causing the leak, im going to try and repair it tomorow, if that fails, il buy another, so if anyone has one for sale, please let me know, and also if anyone has any advice on repairng one of these please post a message, and advice is much appreciated.