i bought a bgf 66 off ebay about a month or two ago,and just recently got my wifes three wheeler frame done,and put the motor on,it started at first,ran pretty good turned it off,let it sit a few, and retourged the head ,which was pretty loose,tryed to start it.and it back fired or popped and would only fire every once in awhile.so i pulled the head and noticed it spitting fuel and oil out of between the head.so i put my spare head gasket on it ,it fired rite up and then popped,and when it trys to fire it makes the typical head gasket squeak ,pulled it back off and sure enough oil comming out of between the head? this is a brand new motor any suggestions on how to fix this?thanks in advance