Super tigre G51not firing up

I have a G51 that feels like it has almost no compression (it was given to 
me as a freebie by a friend). It is fairly new and on disassembling the 
piston/liner look fine with no scratches or other obvious signs of wear. I

have tried getting it to run (using 10% coolpower) and an APC 12*6, but
have 
had no success so far it will barley even fire up let alone stay revving
to 
allow some kind of tuning. I've never had a ringed engine before so I'd
like 
to know should I give up on it or is there something I can try to get it 
running?

All help/advise gratefully appreciated.

PS I have installed a new Enya no.3 plug but no change.