Gas in the oil comes from a bad petcock. With a bad pet cock it can't stop the flow of gas to the carbs.
The float and float valve are not fuel shut offs, they are metering devices. They control the fuel level in the float bowls when the engine is running. As the gas over flows the float bowls it runs into the engine, collecting in the crank case, thus the gassy smell of the oil.
Fix your petcocks.
Clean the carbs.
This excess gas in the oil, dilutes the oil. This cause excessive engine wear if run that way. One of these excessive wear points is the rings. This will cause low compression.
But if adding a oil to cylinders doesn't bring up compression, this indicates poor sealing of the valves.
I might suggest removing the exhaust headers and carbs. roll the engine over to open each valve. Watch each valve to see that it opens and closes fully. Sticky valves could be part of the problem. Use a cleaner, carb, brake, whatever and a wire tooth brush and clean off the valves and seats. Reach in through the intake and exhaust ports.
Once clean, set the valves to proper clearance or a bit looser. Set a bit loose you know the valves can close fully. Once the compression test is done set the valves to spec. Spray a bunch of oil in around the valve springs and valve stems, this should help fix any sticky valves.
If you have a good penetrating fluid, spray that around the valve springs and into the cylinders. If you don't have any, get some ATF and acetone at the parts store, acetone is in with painting supplies. Mix the acetone and ATF 50-50. Makes the best penetrating fluid ever.
This helps loosen sticky valves and rings.
Leo