Lawn mower makes an intermittent very loud screatching noise when in use. The start pull cord loosens slightly when this happens and there is some vibration from around the pull cord casing.
I think you'll find that's the make of the engine rather than the make of mower - perhaps a Sovereign or some such, powered by the B&S. If you have to get spares for the mower, rather than for the engine, you'll need to identify the make.
Does it have self-propulsion? If so, it could be the drive belt - runs round a pulley on the shaft above the blades and back to a pulley on the axle. There's usually a belt tensioner - often at the back of the mower and revealed when the grass box is removed - and a tightening of that may solve the problem.
Very common - The pull start clutch shaft needs lubrication. Take the pull start cover off. Pry the metal cap off the clutch - now remove the ball bearings. Now remove the square drive - lubricate the shaft with a small amount of grease. Not too much or it will run down onto the balls and they won't work as a clutch. Reassemble and make sure the square drive only turns in one direction. They can size to the shaft and alas it is part of the crankshaft, in which case I would take it to the dealer. BTW I've fixed lots of sized ones - you don't really need a new crank shaft!
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