Chainsaw Repair

I have not had the saw long. A guy I know gave up on it after taking it to 2 repair shops without having success. I recommended he try a new 261 ms. He will never go back to using the Jonsered now. So it is a project saw for me to figure out the problem. I to run a 261 ms and a 2165. I will donate this 2054 to my son in law  if i can get it to work properly. I think the main problem with the saw was the tank vent. Just can't understand why it works bad in one position. I take on projects like this to learn.