I have a Craftsman 16.5 b/s ohv engine, carb. Is working, spark plug fires, but has low compression and gas in the oil. Worked fine, shut off 5 minutes then would not start back up.

If you have gas in the oil, the problem is in the carb. Your needle valve hung open by a microscopic piece of trash, or rust, flooded the carb. And the excessive fuel run into the cylinder and seeped into the sump pan.
Remove spark plug, turn engine over and the excessive fuel will SHOOT out , then replace spark plug, start engine. Remove contaminated oil. Change fuel filter, clean carb. Clean fuel tank and lines. And to prevent this in the future add an inline fuel shutoff valve and use it.

Thanks MOWERMAN2468,going to try your recommendation.I'll let you know how it goes.
Wingnut35

Just pay attention to where the parts are. And to remove the welch plug, use a sharpened 5/32" punch and punch a hole into welch plug and pry out. USE CAUTION, YOU DO NOT WANT TO HIT THE PLUG TO HARD AND PUNCH A HOLE THROUGH THE CARB BODY. no i was not yelling, i was wanting that sentence to stand out. then after the cleaning, use CLEAR FINGER NAIL POLISH to "paint" around the edges of the welch plug. To install the welch plug, use a blunt tool and just hit it until it flattens out.

I'm getting a little popping through the exhaust like it's going to start but only when the choke is on.
Wingnut35