A Old Lawn Mower That I Have Works Great She Starts Up In Just One Pull But?

my mower starts and will run if you leave up to the exhaustion of the gas, but it makes the noise of grinding hard and sharp. something is jammed as I looked out and it assumes that this is not anything to be there is he? im thinking its the magnet, but I'm not working on lawnmowers i work on semi-trailers. any thoughts or help would be great thank you.