Guy down the street got a 90's Shadow and it was burning oil at almost a qt per 2 tanks of gas. He was happy to have the bike, but then replaced the engine from a pulled on on eBay.
IDK how much work it is to swap an engine, but I think he was into it about 800~1000 and I think 200 was labor for a guy off CL to come out and do the swap.
So what you can do is put a foam cover over the filter or in the box. My other bike had a foam filter only and they tend to flow well. What you're trying to do is to block the oil, so a screen or very course foam will do the trick.
Performance shops sell "fuel cell foam", I bought it for a carb to keep the fuel from splashing around. It's very course foam that doesn't get eaten up by gas.
Here's a close up view: https://www.amazon.com/Jaz-Products-...49696958&psc=1
Notice how course it is, it would be VERY high flow.
Get a block of that, place it in the box and it should catch most of the oil and keep the filter pretty dry. Remember, the air is flowing the other direction, so shouldn't be that hard to keep it dry.
My guess is that the oil would be coming from an intake tube from the crank case. Had an old Toyota that has a folded up mesh screen in the valve cover (from the factory) that caught the oil being pulled in from the crankcase.
The plugs are a bit more of a challenge, maybe a different heat range? That's just a wild guess, but maybe more exposed or you can spray in some cleaner every so often.
Basically, it's an issue of finding the source. If it's from the crank case into the intake path, that pretty easy to solve with foam. If it's past the valve guides, new valve seals will do the trick, if it's from the rings... don't have a good solution there unless the rings are locked up and you can soak them free.
I simple blow by test will tell you the source.
I thought there was some trick to blowing out the spark plugs, but I don't remember how. Maybe something like a forced downshift, the hit the gas. I think it was an old muscle car trick to flush out the build up after a few runs.