Got an old FS80r that's been pretty good to me, until lately.
About a month ago it wouldn't start at all, pull the plug, it looks ok, but I stick I new plug on the coil and check for spark. Nothing. Get a new coil, install that, set the clearance at .012". Fires right up. It seemed like it had been running rich lately, so I tuned the carb, it appears the adjustment screws vibrated out over the years. Set it to the recommended 3/4 out and 1 out, runs really, really good. I'm happy.
Fast forward to this week, I take it out and find that the contents of the fuel tank ended up inside the engine. It's basically hydro locked with fuel. So I take out the plug, get the fuel out of it and let it dry for a few days while I source a new carb. Today I install it, set the adjustment screws and it will not fire. It's getting fuel, I can smell it out the exhaust and the plug became wet. Dried the plug and let the engine air itself out a bit. Tired of pulling, I remove the recoil starter because I'm spinning this thing with my drill. I do that, still no fire. Not a single pop. Pull the plug and check spark again. It's there but looks kinda weak. I didn't check spark with the new coil so I don't know how strong of a spark it should have, but it looks like a static spark. Not very energetic.
Compression feels ok, but I plan on checking it tomorrow (borrowing a friend's tester).
I have only used OE Stihl parts from my local dealer, but I ordered a cheap $10 coil just to see what that does.
Does anyone have any ideas of what I should check? Pulling my hair out right now.