I agree it is probably something with the battery or perhaps wiring as a good place to start. However, I had a similar problem with the 2007 Sporty and did all the things you are doing and it turned out to be my fuel pump and in fact there was a tech note about the filter screen used in the pump that would change characteristics after even a short ride. It would restrict the fuel flow during a warm start. Mine would be hard to start, sputter a bit and finally take off. I got the fuel screen replacement kit and never had the problem again. I know this is for Sportsters, but you might want to check your fuel pressure. You never know, could be your problem as well.

Here's the tech note:

Originally Posted by cHarley
Here is an excerpt from a HD Tech Tip....

TT328 – August 9, 2007 – 2007 XL Fuel Pressure
2007 XL Pressure Regulator / Low Fuel Pressure
With the help of the dealer network we were able to isolate some recent no start and poor drive quality complaints caused by inadequate fuel pressure. On some ’07 Sportster models the fuel pressure has been recorded well below the service
requirement of 55-62 PSI. This finding lead us to the conclusion the pressure was bleeding down past the large pressure regulator o-ring.

In order to ensure proper positioning and minimize movement of the o-ring a new service kit has been introduced. Use labor code 7164 and order part number 61005-07, which consists of a “Castle” Washer, Filter Screen, 1 Small and 1 Large O-Ring and is
intended for use on 75268-07/A/B Sportster fuel pumps. The “castle” spacer is installed with the openings pointing downward to prevent fuel flow restriction and should be only added to 75268-07B or earlier XL fuel pumps. Inspection processes were put in place prior to 2008 model launch, and in late August of 2007 XL production will be making a running change to a 75268-07C fuel pump. These fuel pumps will not require the “castle” spacer. The original regulator service kit (p/n 61015-04A) will remain available for situations requiring regulator replacement, service of a 75268-07C fuel pump or service of an already upgraded -07B and earlier pump.



Cheers,