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June 9, 2019 at 11:35 pm
#176994
You might want to try soaking the pistons and cylinders for a while with Sea Foam to help break up or dissolve any sludge or carbon buildup which may be causing the rings to stick. These motors used automotive oil mixed with the gas back in the day and it was terrible for leaving carbon deposits everywhere.
Running on a stand but not in water can also be caused by poor sealing in the crankcase. Using a heavier oil, such as a 40W aviation oil, can help to seal any worn crank bearings.