I purchased this motor that hadn't been run for ??? years. I replaced the plugs and completely cleaned the carbs. The motor ran perfectly. After a while I re-started the motor and it ran like a dog. I had to install a new fuel hose to the top carb. I noticed a lot of air bubbles in the clear fuel line. Could this be causing the motor to run bad? OR What could be the problem? Thanks in advance for any help. 