Thanks for the parts diagram but I am nor sure if it helps with my current problem. The problem remains where the other pipe from the fuel tank should go. It is definitely not to the carb with my saw. IT seemed to be coming from a gap in the casing that led to the lower side of the engine. There is a brass ferrel in the pipe and I have convinced myself that it is some sort of system that uses pressure from the crankcase to pressurize the fuel tank but I am not sure where I got that from! Fact is despite pressure washing the engine, I just cannot see where the pipe should go. Any suggestions would be gratefully appreciated.

McCullochs are very famous for vapor locking.One way to see is to loosen the gas cap after the saw dies,let the pressure out of the tank,retighten the cap then start it back up.If it starts back up and runs ok then its vapor locking.Like Sasquatch Man said,the tank vent may not be working right.Sometimes you can take a small bobbi pin and clip it on the fuel line and that will keep a saw from vapor locking.Dont ask me how or why that works,but Ive done it and it really works.I had an old 79 F 250 pickup that vapor locked bad and I put a wooden clothes pin on the fuel line,problem solved.Never found a clothes pin small enough for a chain saw so I used a metal bobbi pin,sure enough,it worked.Hope this helps,Doug

Check some of the "shorten chainsaw chain youtubs" and etc. I saw a number online as the one below that was hard to hear. This should be an easy find and east task. Quick tips that I use with general equipment vs the better tools: 1. I grind the head off and punch out the links to break/remove (after checking close of how many to rem. 2. With the breaks, I�ll know the exact size to obtain from the supply shop to join the chain back. 3. I brad the new link in with a hammed to "0" play (not tight or loose). http://www.bing.com/videos/search?q=shortening+a+chainsaw+chain+youtube&view=detail&mid=6D5573494D25856A776B6D5573494D25856A776B&first=0amp;qpvt=shortening+a+chainsaw+chain+youtube

What have you done related to finding the problem? Such as: 1. Disasemling, inspecting and cleaning the carb for restrictions all ports/screen, bad diaphragm and etc. 2. Replacing all fuel lines, primer bulb, fuel filter and clean fuel tank if needed. 3.You should see some fuel in the bulb and see it moving while pumping or that's restriction IMO. Good Luck!