Had a low end throttle response problem with my 2005 DRZ250. Tried all the normal soutions such as idle screw, idle jet, needle position etc and nothing improved it. My 2001 DRZ250 has fantastic throttle response with all the same settings that I had on the 2005. So I really looked closely at the carb on the 2005 and noticed that when I twisted the throttle no gas squirted into the carb in front of the slide that happened on my 2001. I found that the brass tube that goes from the accelerator pump port in the float bowl to the position just in front of the throttle slide that is suppose to provide a squirt of gas when you hit the throttle did not have a hole or notch in it to allow the gas to travel to the position it was intended to go. It was not clogged, it was never drilled or cut to allow the gas to travel through it. I don't know if that was intended to be that way on the 2005's but as soon as I very carefully cut a small hole into the tube to allow the accelerator pump to actually shot gas into the carb the problem was solved. Throttle response is fantastic now. Worth checking if you are having a problem. Just take off the air cleaner boot so you can observe the inlet to the slide area and twist the throttle. I you don't see a fine mist of gas shooting at the slide, you too could have a carb with this problem.

Great info! Thanks for sharing!