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'05 525 EXC with a miss.

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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.

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What are the letter designations on the needle?? IF the 3rd letter is a "E" put the 155 main back in!

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The needle is a OBDTP. The carb is a 3900B

A 155 main jet with an OBDTP would have been insanly lean. That needle is pretty good and with your 178 is an acceptable combo. It will run stronger and cooler when you get the JD but I don't think that is going to fix it, something else is wrong.

First thing I would check is the spark plug cap, pick up a new one and make certain it is on the wire securly

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I'm pulling the carb tonight to go through it. I already put in a new spark plug and checked the gap. I'll go ahead and look into geting a new spark plug cap.

Could the TPS be effecting it? It idles fine and runs well at 2/3 to full throttle.

I think I'm going to hold off the jet kit until I've gone through everything else.

Thanks for the help.

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