KDX Power Valve

If you never cleaned a 91's power valve, chances are you broke it. Take the pipe and power valve cover off then start it. Does the actuator turn? Then remove the actuator gear, the nut is left hand thread, hold the gear in place with a cresent wrench and remove the nut. Now look in to the exhaust port and manually actuate the power valve. Does it open and close properly? Chances are either the shaft or gears are bad.

i used to have a 91 kdx200, my suggestion would be to get a service manual, i have one actually, i do have a scanner so if you wanted i could probably email you that section, but you will need to take the top end apart to clean it, meaning take off the head and take the cylinder off of the bike, my email is jamin326@hotmail.com, also how is your jetting, that can affect roll on power

Yeah I recently took the top end on my '88 kdx apart (for the first time) and cleaned & serviced everything. My exhaust valves were almost completely clogged with carbon build-up. When I got it back together, I discovered that my bike does indeed have a powerband! :) I'd suggest taking your top end apart and inspecting everything.

Clogged powervalves will not cause the bike to die from abruptly opening the throttle from idle. That sounds more like a fuel delivery problem. Could also be from low compression. Do a compression test. If its low you can clean the powervalves while you have the top-end apart for piston & rings. If the compression is ok you might check for leaks in the intake boot. Did you recently have the carb off the bike?

Leaks in the intake boot will not cause the bike to die. Conversely, they will make it seem like you have a drag bike. If you haven't cleaned the powervalves, I'd suggest doing so, but that won't cause your bike to die either. My buddies '94 was missing most of the powervalves assy. It only died at high rpm. On the other hand, broken reeds and or a collapsed pipe will cause it to die. Check your air filter, has it been cleaned? What about your spark arrestor? If your bike has the original pipe, they were double walled. The inner wall has a tendency to collapse, in essence stopping your exaust. No matter what, clean those powervalves before you wind up with an expensive repair from them breaking. :whiner: