I have an old McCoy red head .19 engine and it's very hard to start. The fuel tube was taken out once and I don't know if it was put back in the right way. It has a very small hole in it and I don't know if the hole is supposed to face downward or straight backward toward the crank case or somewhere in between. I think the position of that small hole in the fuel tube has a lot to do with how it starts and runs. How do I adjust that?