I’m the first to admit I’m mechanically challenged so I’ll try to keep this brief but I’d really appreciate input if you can suggest what my problem might be. At least that way I can point the mechanic in the right direction when I take it in.

I have a 2005 DL650 with just over 85,000 klm and I’m meticulous about service and maintenance and it’s always run really well. I do a lot of cruising at highway speeds (130 to 140 KPH) and I’ve never had a problem. Last week-end I did a two-day ride of 1,100 klm to go out of town for work. On day one I was running low on fuel in a rural location so I had to gas up at a small no-name gas station and right after that I noticed a real drop off in power at around 5,000 rpm. Even at full throttle the best I could do was 120 kph and even at that there was a lot of hesitation. I figured I picked up some rust in the cheap gas so I added an expensive gas treatment to the next three tanks and by the third tank it seemed back to normal.

The bike then sat for a week and this week-end I repeated the trip in reverse except the hesitation is back but this time a little different. I can get up to approx 140 KPH as long as it’s dead flat and I don’t go past ¾ on the throttle but in every gear as soon as I twist to full throttle there’s an immediate hesitation and drop off in power. It feels similar to the problem last week but this time it doesn’t seem linked to a specific RPM, instead it’s very specific to ¾ on the throttle.

Before I turn it over to my mechanic with a general WTF can anyone suggest what this might be?
Thx in advance
Dale

I talked to a good friend of mine who is an expert on all things mechanical and he thinks it's the fuel pump again. I'm just about to put it away for the winter so I'll do a basic service now and in the spring I'll install the external fuel filter mod I've read about.
Cheers

It certainly sounds like a fuel contamination issue from your description. I'd suspect water rather than rust as the culprit. Water doesn't readily pass thru the fuel filter and can act like a dam preventing the fuel to flow. If this happens, the injectors get starved and you'll have a lean mixture to the point that the engine runs horribly. What's worse is that a lean mixture can like an acetylene torch on top of your pistons. Section 5 of the factory service manual talks about the fueling system and components and how to remove and service them.