I did a leak down test on my 717 with help from Mikidymac, I took the carbs off, used a piece of old inner tube to sandwich between the carbs and the intake manifold, took the exhaust off at the exhaust manifold and again sandwiched inner tube in there, and then pressurized to 6 pounds I believe, I would have to have a look at the manual or my HX thread to be sure on the psi, pressurize through the pulse fitting on the crankcase