American-made Briggs engines are not really prone to giving serious trouble unless seriously abused. I don't think I have heard of one throwing the connecting rod unless misassembled, underlubricated or overrevved. Blue exhaust smoke reflects ring or bore damage, associated with bore or ring damage due to underlubrication, severe wear, or sometimes abuse through running rich or using starting fluid or excessive priming. The situation is different with the Chinese-made engines, but older Briggs engines have a very good record for reliability and durability. Problems can just about always be assigned to the causes I have listed, all of which except sheer long, long service can be described as abuse, neglect, or both.