ORIGINAL: JohnW
A full throttle dry run would be very dangerous on a YS and probably other 4-strokes, as it could cause the engine to seriously backfire, throw the prop, or even break the engine.
You're right there, I wasn't even thinking about 4 strokes because I've never used one and they don't collect fuel inside the crankcase anyway. But with a 2 stroke at idle there's very little turbulence to sweep up the excess fuel and send it on up into the cylinder. That's why they stutter and fumble if they idle mix is a bit too rich when you open the throttle. More air gets let in which sweeps up that excess and it's suddenly too rich until it gets burnt off. If it's done at full throttle then there's a lot of air and turbulence plus when the mixture gets too lean for the engine to fire then it takes a short while for it to run down to a stop, maybe another 100 revs or so, which should clear out the last few drops.
Actually this is the way all CL engines stop at the end of every flight and rusted bearings are almost completely unknown in them. OK, I'll admit it
, when I first heard about rusted bearings I started to wonder why it only seemed to happen with RC so I figured the only real difference was in the way the engines were shut down. Plus the common use of castor in CL...draw your own conclusions