My fuel lines disintegrated so I changed them. Now won't start. When I press primer bulb it goes down but will not come back up so I guess there is a vacuum problem, the bulb pushes air through the line into the tank but it is not sucking gas in which would make the bulb come back up? Is the filter clogged or something in the carburetor not allowing the gas to be drawn up from the tank. Is the carburetor hard to clean out?