Welcome to the forums, the bike and its nice to see another Washington rider on here, and even better that its a Washington rider on a KLX, I mean that's the perfect combination. Where are you in the state? Too bad you couldn't get the number from the dealer for the previous owner so you could ask him questions. I wonder if the bike shop even took off the seat to see the lid gone?

 

If the air box lid is off and it had aftermarket exhaust you would think the jet size would be larger than stock. I would start by checking the plug to get a base to start from. It could be someone did the mods and never re jetted. Just thinking out loud.

 

You need to check the plug. Put a spark plug wrench in your pocket, warm the bike up and run it down the WFO. Pull the clutch in as you hit the kill switch and coast to a stop, then pull the plug and check it. I bet it will be white indicating lean. Probably easiest to order the Dynojet kit rather than trying to scrounge up the part numbers for the individual jet and needle.

 

I looked over the carb real closely and it appears the float bowl screws have never been removed===the idle mixture screw has a metal cap covering it====which tells me the carb hasnt been messed with=====at this point I think I am going to leave everything alone---------I am going to buy a FMF Q4 for this thing then at the same time I will install the dyno jet kit------this bike is such a DOG right now=====I was able to wheelie the front tire 6 inches off the ground in 1st gear from a rolling stop====THATS SAD====also it seems when I rode it today that 8,000rpm was the point I feel the most surge/power loss======but the bike seems to have ok low end power=====it accelerates right up to about 8,000rpm ====but I tried to go higher and the bike didnt want too======but anyways that useless muffler cat converter assembly have to GO in the garbage=====and then the jet kit and a 13 tooth front sprocket and this bike should ride like I want it too from all the reading I have done..........even with the power surge=====I think I am falling in love with this bike LOL========my first dirt ride is going to be this weekend--------and the bike will be stock still====I cant order the FMF pipe until next monday=======If anyone thinks I am on the wrong path here PLEASE let me know ======I appreciate all your guys responses and help======

 

if nothing was done and the air box lid was open that is most likely the problem, otherwise the spring in the slide is fluxuating from improper vaccume pressure with the ballance of the spring and intake vaccume.

 

UPDATE UPDATE UPDATE================I built a false lid for the airbox----since mine is gone========I drilled two 1-3/4" holes in the false lid====bolted it on=====and it instantly fixed the high end surge======I actually pulled a big OL wheelie========I will remove the false lid once I get my new exhaust and jet kit=====thanks for all the help guys===RIDE ON