davo so sorry to hear yer problem. i hope yer hobbyshop or someone who sold u will help u there. i got mine so tight..yes very tight as when u push the piston, the sleeve will come up. after 20 tanks of run-in & racing 45minutes main.. it still got tons of compression.
i think u better ask the person who sold u this. if u say ur engine is not tight at all when u just got it..than thats the problem. big problem. u must've been cheated.