Milky bottom and low coolant level seems like contamination. Might be a head gasket leak so tear it down anyway. Clean the carb in straight vinegar if it's been sitting and is hard to start or won't idle. Leave the rubber alone. It won't swell like chem-dip or the more industrial strength carb cleaners.
Drain the crankcase and wash it out with kerosine and fresh oil. Then dump the mix and change to your regular oil on your rebuilt road test around the backyard.
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