Yup. 
When I drained the fuel about six weeks ago and filled it with Aspen.  It would not start.  Fuel was getting to the filter, I could see it.  It was not getting past the filter.
Turns out the crap fuel we have these days also has a tendency to clog paper fuel filters when it gets to be a few months old, exacerbated by fuel stabilser apparently.  I did not know this until I started watch vids of teryl dactylI, who owns a garden equipment shop.  This is why briggs and stratton do not recommend paper filters.  Gauze only.  Stabiliser slightly gels the stale fuel and can clog very fine paper filters when stood for long periods. So  I am done with inline filters.   
Anyways, I blew back through the filter ( not a cheapo, it is a Wix) and it cleared with a pop.
Bike duly started and ran well.  I made a vid of it at the time.

Parked up smug in the knowledge that my fuel issues were over.

Decided to start both up yesterday.  Little yeller started first prod.  Yay.  Result!


Turned my attention to the devil bike and noticed a small coin sized puddle of something underneath.  It was fuel and it was dripping out the carb overflow tube.
What, how?  Fuel was turned off.

Pulled fuel line and looked at the tap.  It was leaking about 1 drip a minute.  Ok.  I will start it up and empty the carb. Drain the tank and order a new fuel tap.  The old one is only 2 years old, but may have been a cheapo one. I guess the ethanol got to the valve sealing washer.  Either that or Aspen is more searching than regular fuel and can make its way past worn seals that normal fuel cannot.

Ignition on, choke on.  Kick. Kick kick kick.  Nothing.  Removed plug.  Absolutely sopping wet.
Dried plug.  Kick kick.  Nothing.  Removed plug, absolutely sopping wet. 
The feckin devil bike has done it again.  It comes up with ever more complex scenarios to screw me over. 

So this time we have a very slightly leaking fuel tap.  This fact was hidden by a plugged fuel filter. Fuel filter unplugged and bike started, fuel changed over to stuff that will not cause damage or go off.
Fuel leak slowly made its way past the needle valve in the carb, it is rare for a float valve to be 100% fuel tight over several weeks. So carb flooded with fuel,  some of which came out the overflow.
Because Aspen fuel has very little odour compared to regular fuel, the leak was not detected by smell and because the leak was so slight, it was evaporating almost as fast as it dripped.

Of course, this being the devil bike, the crankcase has also at least partially flooded with fuel.   AAAARGH.

And the DT does not have a crankcase drain plug.  A poor state of affairs for an off road bike...

I see a session of pushing it up and down the street with it in gear and plug out in the future.  I have had a lot of success doing that with waterlogged bikes in the past.

I will have to wait for my busted ribs to heal first though.​​​​

A tip I've read, I think, from Morley (or I might be adapting his tip for some other problem!), but how about using an electric drill, clockwise, on the bolt on the end of the crank, with the plug out. I did this on my R5 and I think it worked ok.

Your Devil Bike remined me to change my fuel filter. It's been on for a year, subjected to the standard 10% ethanol 91 octane gasoline here in California, but has held up beautifully. The first tiny filters I used came free with an air filter, and had a thin paper element. It wasn't long until I noticed the element floating around detached, like a snow globe.

The first cheap aftermarket petcock I used looked nice, but I walked out into the garage one morning to a strong odor of gasoline. Like yours, it had a steady drip when turned off (but more like a drip every few seconds) and I later discovered that my old original carb float was sinking like the Titanic. Got a new float and Yamaha petcock for the Grizzly, cut down the tall tube, and it's been working well for over a year.

Pushed devil bike up and down the street for a couple of minutes, p!ug out.

Drained tank, replaced fuel tap.  Put spark tester on for good measure while in the area, to make sure it had spark.  It did.

Plug refitted.

​​​​​​Kicked it over till it started, then ran it till the carb and crankcases ran dry and it leaned out and stopped.

 Put a litre of Aspen back in the tank and kept an eye on it for five mins to see if it was leaking.. Nope.

Checked to see if a litre was enough to cover the stack pipes- it was.  Turned fuel off and observed tap again for leaks. Nothing. Fitted new fuel line without filter.

Second kick and she is running again and sounding crisp.

Until the next BS "fault"

Devil Bike cleverly made you think all is well, but it's scheming it's next dirty deed as we speak...

I dread to think of the next escapade.  That bike is positively machievellian.