2003 450 FSE Died Suddenly and No Longer Runs Right!

[cruzer555]

So I bought this 2003 FSE 450 supermoto in March because I thought it looked like fun. Little did I know exactly what a rare and obscure bike a Gas Gas supermoto was.

Here's some background, so the entire time I've had it, it ran great up until this week when the problem started. I only rode it once prior, for about 25 miles, but I ran it a good several times and took it up and down the street.

The problem occurred a few days ago when I was taking it for another ride. It started easily as ever, in only 4 cranks it was purring like a kitten and ran great as usual.
But, about 9 miles into riding, it started to sputter a little, like it was running out of gas, but I had topped it off and it had plenty. I kept riding for another half mile or so in the hopes it would clear up, but instead it lost power completely and I coasted to someone's driveway.
Occasionally while waiting for the tow from my friend I would press the starter to see what it does, sometimes it would crank with no fire, sometimes fire a little. But it never ran.

Then I went to the garage to check on it 2 days later, it cranked and cranked, nothing. So I left it a couple minutes, checked the battery (it's lithium and has a built in indicator) and tried again. Fired up and idled. Seemed almost normal again actually, it idled and I could rev it. It did stall once but started back up. BUT, when I took it just one block up the road and turned around to come back, she DIED on me again same as before!

I don't even know where to start with a fuel injected bike like this. Has anyone had a problem like this? Any help would be appreciated!