Thanks tezza and Grumpy. Will try your suggestions now and post result. It does seem to me like a broken conrod. As for potential crankcase damage, how to pick if there are no leaks or obvious external damage? Does it need dismantling and examination with a magnifying glass for fine cracks?


PG
My Mowers:
SB Model 45: 17",3hp, Model No:21339, B&S Model 80202, type 1735-01, Code 82111901
SB Model Diplomat 430: 17", 3hp Model No:1414, B&S Model 80202, type 0880-01, Code 79110101