You wouldn't think there would still be "undiscovered" trails in WA. If you can call a DNR built ORV trail "undiscovered". But I've ridden it twice and haven't seen a soul much less any motos. Granted both times were in intermittent pouring rain in April. There's enough out there now to make a destination 3 day weekend out of PA, especially when you include Dungeness and Quilcene and a few things I can't mention here.
https://www.trailforks.com/trails/sadie-creek-orv/
https://www.trailforks.com/trails/sadie-creek-orv/