If the exhaust hole in the engine has a recess it needs a gasket. If not the gasket is already in there. Sometimes the gasket gets smashed down and carboned up so much it looks like part of the cylinder.
The springs from header to pipe should go from top to bottom in a spiral. If they go straight across they can vibrate and fly off.
There should be some kind of pipe mounting stem coming off the left bearing area. You use this to mount a pipe cradle hopefully with some kind of flexible rubber grommets.
You can stretch the cradle springs by grabbing them with vise grips or they make special spring hooks with a handle.
Hope that helps,
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience