One of my ultralight deadsticks was a real head scratcher, it wasn't until I took the bowl off the carb that I found what looked to a be full grown house fly in there that had caused the fuel flow problem. The only thing I could figure is it got in there as a baby and then grew, but that didn't make any sense as I flew that thing a lot and often. That one still confuses the hell out of me.
Another Pterodactyl one had the engine running great (no tach or other gauges, just going by sound) but down I was going......the only reason I got off was the 14% grade on the strip I had then and the descending terrain below. All I could figure was some sort of freakish early AM down draft at my mountain site, it just wouldn't stay or go up, just big smooth sink. Now a normal dead stick was routine, but in the confusion of the motor sounding great with lots of r's, I got behind the curve and plopped her in so hard both main gear axles sheared off and bounced back in the air and didn't land until the dust cleared, every tube in the airframe bent, every thimble in the 3/32" top rigging was elongated/ stretched, the 4' x 1" kingpost had a double compound curve from the compression forces, and I got a minor cut lip from getting my knees jammed up (and this has been my worst injury in 42 years so no complaints). That's when I learned to make sure the prop, after a late night emergency repair, was re installed the right way, and not back asswards. Another time a buddy had his sleeping bag get loose, and it got sucked through the prop and down he went. He was stuck there for the night, and with no sleeping bag

Another time another buddy sheared an axle landing out, and pulled a fencepost out of the ground and with it safety wired on it got him out of there. He kept that post in his hangar. Actually, I think that was all the same occurrence and the same buddy. I keep finding rocks in my baggage area, keepsakes from high alt off airport sites, but then I fly around with them for a month or two before setting them on the deck trophy shelf
It sure seems like a lot of fuel valve switching problems, I see no reason to switch over (pun intended) from both damn tanks feeding a common line all the time, period, and I never shut my main valve off, period. That way I never run out until I run out, period.
