2007 Troy Bilt 13AN77TG766 with B&S 17.5 OHV Itech 31C7070603 E1 I have had this machine for 2 years strong engine till it blew head gasket. I changed head gasket and ran 2 or 3 hours and blew another gasket I could wigle piston so I tore it down honed it out and replaced piston and rings, found out my head was warped so bought a new head to put on it, the shroud had broken blades so I had another engine same model but different way the shroud attached and had to use 2 bolts on flywheel to attach and they were rusted and broke off so I use flywheel off the spare engine and the armature. I tried starting it and it was hard to spin and was told it was the pressure release on the cam so I bought a new cam and put it in, set the valves at specs 4 intake 6 exhaust cranking was great but then gas was blowing out the breather that was from stuck float fixed that, checked spark and it is great got good compression cranks normal but won't start. I've been on this thing every day for 3 weeks I'm frustrated as hell if I had some dynomite I would blow the thing up. I put my hand over breather inlet and it will suck in then push air outwards in out in out is that normal I thought the carb just sucked in any help?