Thanks- currently the engine won't run without the choke on and the idle high... and at that, it has little power. My boy ran fuel/oil mix through it, and that's what it's been doing ever since. I disassembled and cleaned it to no avail- and wasn't sure if the tube missed it's connection.
Is the air filter clogged with the 2 stroke oil? Fouled spark plug? Choke on after warmup usually means lean, but needing to turn idle high means rich. Did you get the float set right? Have you done the proper air leak test? Maybe the exhaust got clogged from 2 smoke oil? Last, hopefully not it: running oil in the gas without adjusting jets might have made it run too lean and overheat, possibly doing bad things... hopefully not that.
Don't know enough about effects of pre mix on a 4 stroke, but if the filter was clogged the choke would only make it worse. I suppose it could have fowled the plug if it is a much colder range. Worth a look.I doubt it would have caused enough of a lean condition for damage. I would be more inclined to suspect a coincidence and the intake just happened to loosen during the time the pre mix was being used.