Weak Accelerator Pump

I have a 2000 WR400. And like a lot of them as it seems, when I whack the throttle open from low rpms, it justs wants to die. I have read many of the post on here about the BK mod and thought orginally that maybe that was my fix, but after looking into the problem, I think my problem is not too much fuel from the accelerator pump but not enough. I removed the subframe and watched as I opened the throttle quickly (engine not running) and noticed that the squirt (more like a dribble) was relatively weak and not very long. So after putting it back together, I started it and manually operated the AP by pushing the linkage down with screwdriver at the same time I opened the throttle and it reved with virtually no bog or stumble. Do the springs in the AP get weak over time? Is there something I can do to fix the AP problem. Any advice would be greatly appreciated.

you might want to dissasemble the carb and clean. The pump on the older models gets really dirty and sticks if not clean.

Please fill us in on the resolution to this issue, I have that same year of WR and I have thought that maybe I need to do the BK mod as well.

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