Just bought a used McCulloch Chainsaw on the cheap knowing that the fuel system needed work. As with most used chainsaws, it had been sitting, and the fuel system had all aged and cracked. So, I bought new lines and filters yesterday, cleaned the saw up, put in a new primer bulb etc... and started running into a issue.
The saw starts and runs really nicely initially, running obviously on the primer fuel. It then dies after a couple of seconds. Keep lightly pushing the primer bulb, and it will keep running. I took apart the carb, and everything looks really nice and clean, but what I don't know about two stroke carburetors fills books.
My question is, "How does it work?"
There was four total rubber lines in the saw, one obvious one going from the bar oil to the oiler system, two going into the fuel tank and one going from the bulb to the carb. For the sake of discussion, lets identify the two tank holes as "A" and "B" and the two Carb fittings as "1" and "2". The primer bulb lets go ahead and throw in here with fittings "I" and "O" for in and out.
The hoses were a mess when I pulled it apart, and broken in several pieces. So, I don't have a guide to go from. I have ordered a new carb kit on general principles, so that is coming, but lets make sure I got the plumbing right to begin with.
The two holes in the tank are just that... holes. The hoses pass through them to seal them. So, I have no idea how far to pass them through.
The filter came out of the tank on a longer hose, so I assume that the filter needs to be in the bottom of the tank, and that it goes to the bulb.
I have plumbed it like this... "A" goes to a long hose to the bottom of the tank and to the "I" fitting on the primer. From the "O" fitting on the primer I went to the back of the carb (Fitting "1"), to a fitting just below the idle circuit needles, and into what appears to be, once pulled apart, a diaphragm that controls a needle and seat valve. On the forward part of the carb there is a 90 degree fitting (Fitting "2") that didn't appear to go all the way into the tank bottom, and I assume is some kind of vent?
Bottom line, it doesn't work, and the carb didn't look that bad. Did I mess up the plumbing?
PS... How do these things pump fuel?