Piston Kit Briggs Vanguard 16HP 479cc 68mm 843951 305447

Piston kit for the Briggs & Stratton Vanguard 479cc V-twin, replacing Briggs part number 843951. Bore is 68mm standard. Supplied as piston, ring set and wrist pin. WHICH VANGUARD IS THIS. The 479cc engine is the 16 horsepower V-twin, 29.25 cubic inches, model numbers beginning 295, 303 and 305. Confirmed applications include 303447, 305447, 305442, 305446, 305777 and 295447. CHECK THE MODEL NUMBER, NOT THE HORSEPOWER. The Vanguard V-twin range covers 479cc, 570cc and 627cc and every one of them has a different bore: 479cc - 68mm bore - 16HP - piston 843951 - this kit 570cc - 72mm bore - 18HP - piston 843792 627cc - 75.5mm bore - 23HP - different again The six digit model number is stamped on the blower housing and it is the only thing that settles which one you have. OVERSIZE. Briggs made one oversize piston for this engine, 843958 at .020 inch over, with ring set 843957. Standard ring set on its own is 843953. BEFORE YOU ORDER A PISTON ONLY. Look through the exhaust port with the muffler off. Light transfer marks will hone out. Deep scoring, or aluminum smeared into the cylinder wall, means the cylinder needs attention and a new piston on its own will not bring the engine back.

• FITS THE 479cc 16 HORSEPOWER VANGUARD V-TWIN - 68mm standard bore. Replaces Briggs 843951. Model numbers in this family begin 295, 303 and 305 - 303447, 305447, 305442, 305446, 305777 and 295447 among them. Briggs calls it the 30 cubic inch class, though it measures 29.25. Identify the engine by the model number stamped on the blower housing, not by the horsepower on the sticker.
• WHAT IS IN THE BOX - Piston, ring set and wrist pin. The matching Briggs ring set is 843953 if you are replacing rings alone on a good piston. Pin is 807621 and the pin locks are 690683 if you need them separately.
• NOT THE 18 HORSEPOWER ENGINE - This is the single most common wrong order on this part. The 18HP Vanguard is 570cc with a 72mm bore, model numbers beginning 350, 351 and 356, and it takes piston 843792. A 68mm piston in a 72mm bore is four millimeters of daylight. The 23HP is 627cc on a 75.5mm bore and is different again.
• STANDARD BORE - MEASURE IF THE BLOCK HAS BEEN APART - This is the standard size piston. Briggs made one oversize for this engine, 843958 at .020 over, with ring set 843957. There is no factory .010 or .030 for this family, so a listing offering one is selling an aftermarket piston. Measure the finished bore before ordering either way.
• WHILE THE TOP END IS OPEN - Check ring end gap in the bore before assembly and stagger the gaps on installation. Look at the cylinder through the exhaust port first - straw colored transfer marks will hone out, deep vertical scoring or aluminum smeared into the wall means the cylinder is finished and a piston alone will not fix it. Fit a new crankcase gasket, 845254, on reassembly.