Hey Jim, just read this thread. Lots of good ideas, all of which might be the case.
I frequently had a similar problem (4-5 times a year when the bike sat for more than 2 weeks) and my problem was most definitely just what Mick described in Post #16 . . . Ethanol Phase Separation, aka water at the bottom of the tank.
My solution took about 1-3 minutes, each time it happened. Be sure your battery is charged up before you start.
- ignition on, kill switch off.
- push the start button and hold while opening the throttle up all the way.
- run for about 10-15 seconds, and if it didn't start, stop. Wait 10-15 seconds.
- repeat procedure. Be patient.
- Usually about the 4th or 5th try I'd hear and feel the engine catch a spark or two then kind of chug along. Your almost there.
- Remember the 10-15 second limit.
- Once the "chugging" starts, the engine isn't yet self-sustaining, but it's coming shortly.
- As soon as the engine catches fire, quickly reduce the throttle, but not all the way, and rev to about 50% a time or two.
- Let engine continue to idle, suit up, kick stand up, 1st gear and . . . go.
My non-technical thoughts on what I did was that the amount of water condensed in the ethanol isn't much and I just needed to pump it out enough to get to some liquid with some firepower and the bike would do the rest. I only ran the starter for 10-15 seconds at a time so as not to burn it up and to extend the battery output.
So, I definitely do not have the technical expertise of most of the commenters on this thread, but . . . this is what worked for me and kept me riding. I did use fuel stabilizer one time, let it sit and settle to the bottom of the tank, and it seemed to speed up the process, but it still took several 10-15 seconds intervals of cranking to 'catch fire.'
FWIW,
Shuey