Are you shutting the fuel off at the petcock when you park it? These bikes are known to leak past the needle and seat when parked due to dirt or worn needle/seat. Check your oil level because the fuel will drain into the cylinders and seep past the rings. This will dilute the oil and raise the oil level. Keep the oil level below the midpoint of the sight glass.
The other frequent result of carb leakage is hydraulic lock of the engine which results in bent rods and or broken engine case.
if it hasn’t been done, the carbs should be removed and rebuilt.
Personal experience: I went to start one of mine when leaving the office and had forgotten to turn off the petcock. The starter simply clicked loudly. I removed the spark plugs, cranked it over, and fuel sprayed out of the spark plug holes. I was fortunate in that there was a piston near the top of its stroke with fuel locking it from continuing its stroke. A gap without the fuel would have allowed it slam into the fuel and ruin the engine. So carb overhaul and oil change was mandatory. Now, the fuel is turned off when I shut the engine off every time without exception