I have a vertex .16 and there is a screw that is totally stripped on the back plate and I can't get it off. I was checking for rust because its been up in storage for a long time without after run and I wanted to clean it up. I tried everything to get it off but it still won't come off. I left it outside with the carb taken off on a chair and one of my dogs knocked it off and it fell into the mud and totally drowned in it. There was some mud that went inside so I took WD-40 and drowned it in it so it wouldn't rust from water. How am I supposed to get the mud out if I can't take the screw off? Should I just consider it trash now?

screw extractor?

I've tried it and it doesn't work it just chewed it up more.

Does that mean you already tried to drill out the bolt?

If not, use a slightly over sized torx bit (not a "L" shaped torx). Hammer it in, and if it grabs, it should come out.

if it's a "button head" style screw and not countersunk, put a thin cutting wheel on a dremmal and cut a slot in the screw to fit a standard screw driver.
Good Luck

I used a torx bit and it just made it a lot worse. I think at this point I'm just bathing it in marvel mystery oil and hopefully the dirt comes out. If not, I will just run it until it scores itself and dies. Then I'll get a better quality engine. What are some inexpensive brands that work well? I have a .16 in there right now but I want to upgrade it to a .18

Check ebay. From $80 - $150...

If it is a countersink screw just drill out the head so you can remove the backplate.
If it is a flathad you can drill or grind off the head

I just started it up after I flushed it out with marvel mystery oil. It started up surprisingly even though its been through so much. I've overheated it many times, it sucked in dirt many times, and its drowned in water. It still runs like its brand new and it just never gives up. I'll just burn it out and then replace it.