You may have an oil pump adjustment problem, but more than likely you have a rotary valve shaft seal going down. There are two seals on the crankshaft that keep oil in the rotary valve shaft chamber and out of the combustion chambers. When these seals start to leak, it allows the injector oil that passes through the rotary valve shaft chamber to leak into the cylinders. When this happens, there is an excessive amount of oil being burned. Eventually, the leak will get worse and the engine will constantly foul plugs. A couple of ways to check are to pull the plugs and place a clean rag over the cylinders and turn the engine over. You will see oil on the rag if you have excess oil in the cylinders. Also, if the leak is substantial, you can pull the impulse line from the carb pump and turn the engine over. You will get an oily mist out if at least the Mag cylinder is leaking.
BTW, to check the oil pump setting, stick a mirror under the carbs and look for the oil pump. With the throttle closed, the dash mark on the arm should line up with the dash on the pump. If not, adjust the cable at the carb mount bracket to line up.