Be sure everything is cleaned up, like azhar said. Replace the plug. Check to be sure the needle valve didn't get slightly bent in the crash... that will make the O-ring not seat properly and you'll never get mixture set right on the YS45... been there, done that. Check your bearings to be sure they didn't rust or pit. Check the regulator for gunk and be sure the check valve is working properly.

Don't use WD40 to drive out water... use alcohol instead. I just use methanol you can by at a hardware store in the paint thinner section. Then coat everything with a good YS safe oil. I use Mobil 1 100% synthetic automobile oil (one quart will last a lifetime and it is cheap.)

Water can start the rust process almost instantly. Even 1 hour with moisture can cause rust/pitting on bearings.

High RPM can shorten plug life, but if properly set up, plug should last for quite awhile. On my YS45's, I could run about 3 gallons of fuel before I need to replace the plug. Typically, I burned them in half at high RPM. Sounds like the plug looks OK, but sometimes it is hard to tell if it is working properly... try a new plug.

Cheers