The rattling noise may or may not be related to the motor not starting, but I'd definitely figure out what's causing the noise first. Could be anything from busted ratchet pieces in the recoil mechanism to a piece of debris dragging across the flywheel fan blades to a loose coil to a busted connecting rod down to a broken governor, bad main bearing or loose blade. Since I can't hear the noise, I'd recommend first checking the one of those things that would definitely make a rattling noise and would definitely keep the motor from starting: Remove the spark plug and shine a penlight into the cylinder, noting the position of the piston. Pull the starter rope just enough to make the engine turn over partway. Repeat a few times. If the piston doesn't move, busted rod. That'd be both the source of the noise and why it won't start. If the piston does move, I'd work by process of elimination until I found and addressed the source of the noise. That done, make sure you have a good spark when you crank it. That done, the problem is almost certainly a dirty carb. If your carb has what appears to be a 1/2" nut holding the bowl on, either shut off the fuel valve (if your motor has one) or clamp the fuel line to the carb and remove the 1/2" nut from the bottom of the carb bowl. The "nut" is actually the main jet. Clean it and the bowl with carb cleaner, making sure the tiny holes in the nut/jet are squeaky clean. Reassemble, remove the clamp and try again. If still no go (or it's the older-style carb with screws holding the bowl on) you'll have to pull the carb and do a complete disassembly and cleaning. Dang this was a long-winded answer but I didn't have much to go on. Hope it helps.