We purchased a used trac-vac unit w/6 HP Kohler that was originally mounted on at Exmark ZTR. The owner indicated that the unit may need a carb rebuild since it had been in storage for a couple of years. We rebuilt the carb and tested and bench tested the unit prior to installing on our Bobcat ZTR. Runs good all is well! Pretty straight forward install. A couple of days later we went to test this unit out and discovered all the fuel had drained out of the gas tank into the crankcase. Will this occur if the engine is not mounted level??