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hey, I've got a 2010 250 sx and am experiencing power issues. It will sound boggy and only deliver about 70% power while riding it hard. To me it sounds like I'm getting too much fuel but I've cleaned the carb and changed spark plugs and even dropped the needle. I was mixing it 32:1 because thats what my cr takes and it's always ran good until this year. I changed the mixture to 40:1 and rode it once and it seemed to lighten up the color on the spark plug but the issue is still there. I have disassembled the airbox and completely cleaned it all. I am wondering if it is a ignition thing or if i should rebuild the carb, anyone run into this? It has a stock kehein carb. It sat for probably 6 years and has never been rebuilt
 

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You can run 32-1 if it makes you feel better but it will not make much of a difference to jetting. Your KTM is designed to run 50-1 but richer oil ratio won't hurt anything. Some folks will claim a bit more smoke but it's very slight difference in smoke. If you share premix with your other bikes use what you have without worry. More oil is better than less oil and contrary to wannabe "experts" more oil makes less friction and MORE POWER than less oil. Your leaner oil ratio will run slightly richer jetting. Most 250s won't notice the difference. I suspect your bike is running rich. Check your plug color. If leaning out main jet doesn't make it happy, check jet holder o ring. It will make the bastard impossible to jet and run rich and blubber. Replacement carburetor parts are available from JD Jetting or Sudco. Check back for assistance as needed
 

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When you say "hard" what throttle position does that equate to? 3/4 to WOT? What's the exhaust/power valve doing? What spring color are you using? If this is with lots of throttle open it sounds like your power valve is stuck closed or you're way too rich on the main jet.
 
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