A problem that more and more PC800 owners are experiencing is oil leaks from the air box boots. The boots connect the air box to the carburetors. They are glued into the air box. Over time, this glue eventually fails.
Usually excess oil vapor and overfilled oil is drawn up from the crank case and into the air box where it mixes with incoming air that then is burned in the engine. The tube you see that connects between the air box main body and the lower boot in the photo above developed a large leak. In order to fix it, I used some silicone that I found at the auto parts store. It was rated as being very heat resistant and plastic compatible. The stuff had a horrible smell. I had to keep all of my windows open while working with it. One note of caution is that gluing should be done where you can make sure that the air box will still fit onto the carbs correctly. I didn’t do that and had to manhandle the air box back onto the carbs.