The clean band should be about 1 mm wide on both surfaces. You may have burned the valve if you have been running it like that.īegin by lapping both valves until there is a clean band of metal showing all the way around both valve head and valve seat. The engine cannot be expected to run with effectively zero inlet valve clearance, and if you try it will pop in its inlet pipe, if it runs at all. If you still find very little inlet valve clearance, you will have to shorten the stem of the inlet valve. The Briggs Easy Spin feature holds the inlet valve open slightly during the compression stroke, so you need to set the engine slightly past top dead center on the compression stroke, so that the piston has moved down the bore about 6 mm. Specified valve clearance is inlet 0.006" (0.15 mm) and exhaust 0.008" (0.20 mm). When restarting the engine is started and chugged and after a few seconds it eventually got back up to the required speed.Īs a result of the initial test I proceeded to check the tappet clearancesĪt this stage I am thinking about laping the exhaust valve only and ever so slightly grinding and lapping the inlet valve. Once the engine was put under load it started to pop ever so slightly from the exhaust and once the engine was quite warm (10 mins or so of heaving mowing) it lost some power. Upon getting the engine back together it started pretty easily and sounded quite good. A very good engine from my experience.Ĭleaned the carb and replaced the diaphragm I acquired Briggs and Stratton 375 Sprint Engine (It�s a slightly older briggs with the starter clutch). Got one I am not 100% sure about before I progress.