1999 R1100RT 62K miles. Running beautifully until a fill up and after about a mile or two had some problems, would not idle and had no power to pull hills unless I kept the revs up. Under no load on flat roads seemed to run ok. Got to my destination and it would not start once cooled. Got the bike home and removed all the old gas and put fresh gas in, no difference, I?m now pretty sure the fill up was a coincidence. The fuel pump fires up and pressurizes when the systems is closed and freely pumps fuel through the system and out into a container the few seconds it runs when the key is turned. The plugs are new but the spark looks weak , I replaced the plug wires, the coil measures fine yet I had it stressed tested locally and it works well, pulled the BBS and had a little carbon buildup but not bad. The bike will start by holding the throttle open a bit but runs like crap. I have not adjusted the valves yet but I doubt they would have changed adjustment so suddenly. I have not done a TBS as it is not running well enough to do so but at higher revs the twin max pulls evenly.
I've been through everything and the only thing that eludes me and I don't think is normal is the weak spark. I get a weak yellow or orange spark from the plugs not a nice white or blue snappy spark like I would expect. The weak spark does seem to change in intensity from cold to warm, somewhat weaker when warm. The spark sometimes is more like static and dances all along the electrode instead of jumping at the gapped end. I'm leaning toward an intermittent HES. The HES was replaced 4 years and 30 k miles ago. I did pull the HES and peeled back the insulation to look for the deteriorated wires I had seen when I replaced it the first time. The wires seem soft and pliable with only the faintest hint of the green corrosion you see around electrical connections. The HES also seems ok by the fact that it causes the injectors to spurt and the plugs to fire. When the HES failed the first time the bike just died. This time the bike starts hard and runs badly. Would the intermittent HES cause the weak spark? I know the HES on these machines are troublesome can they fail after 4 years? Should I be looking for other problems?
Other info; Two weeks and two tanks of gas before I had trouble I did replace the fuel lines, filter, etc. I opened it again yesterday just to see if I may have messed something up and it all looks ok.
I do use these forums a lot for help and I do appreciate any help or insight you can give me.