I bought a used '05 525 EXC that was a trade-in at a dealer. It seemed to run fine when I checked it out, but upon taking it out for my first afternoon of riding it developed a bad miss once it was well warmed. It ran fine when WOT or close to it, but when held at a partial throttle it has a bad miss. I put in a new filter and plug in with no help. I checked the jetting and found it had a 42 Pilot, 155 main, a needle from a 525 SX, and the mixture screw was 1/2 turn out . I put in a 178 main and set the mixture screw to 1 1/4 turns out, but my dealer didn't have the correct needle. I'm pretty much at sea level here. Only about 200 feet. However, after my changes it still has the miss and adjusting the needle nor the mixture seemed to have much of an effect. I think my next plan is just to get the JD Jet Kit and pull the carb, clean it and check the float level. Any additional help would be greatly appreciated.