I decided to take it a step further and drill the end cap rivets. It was difficult getting the cap off as there is not much to grab onto. Below are some pics of what the inside condition was like, carbon and sludge. I sprayed brake cleaner inside, but there was still thick sludge leftover. Next I took a torch and burned a lot of it out. This probably would have been good enough, but I was still curious, so I drilled the 2 rivets that held in the spark arrestor. I inserted a piece of wood on the input side and tried to tap the arrestor out the rear but it got stuck at the end. Then I tried it from the rear, Oh Yeah! I took my scrap wood tapping the arrestor toward the the input side, it worked.

Above pic is after I used the torch to clean it.

Above shows the arrestor being removed from the input side.
If I did it again I would use a larger diameter scrap wood to distribute the force over the spark arrestor while tapping it out. That way you're less likely to bend it. I was able to remove it without damage!
Now I need to finish cleaning and see if I can get it back in.