The crank bearings went out on a 440 Xenoah engine. I disassembled the engine and had a shop replace the bearings and reassemble the crank. After putting the engine back together and starting it up, the engine backfires. It has a cdi and stator plate is set on the crank case boss marks. Also coolant leaks out from around the cylinder head gasket, but does not leak into the cylinder. The gaskets are new. Should I have used a liquid gasket on the gasket. And what would be causing the backfiring.