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2004 YZ125 jetting?

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I've searched the forums for info and I'm certain that the jetting on my sons YZ125 is rich. The main is a 410 and our altitude here is 5800ft, so Im asuming I need to be in the 390 area as a 410 is stock jetting at sea level in the manual. Does anyone know for sure? Yes I plan on doing some testing for sure,It ran like crap at rampart this past weekend and I pulled the plug. It was quite rich and the bike ran like crap until it got on the pipe.

Thanks for any info,Snipe

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I've searched the forums for info and I'm certain that the jetting on my sons YZ125 is rich. The main is a 410 and our altitude here is 5800ft, so Im asuming I need to be in the 390 area as a 410 is stock jetting at sea level in the manual. Does anyone know for sure? Yes I plan on doing some testing for sure,It ran like crap at rampart this past weekend and I pulled the plug. It was quite rich and the bike ran like crap until it got on the pipe.

Thanks for any info,Snipe

If it's running like crap until you get on the pipe, you're looking at a pilot jet and needle adjustment as well as a leaner main.

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Ran the bike at Rampart again this weekend jetted leaner at a 380 main and was alot cleaner. I switched needles as well and still have some testing to do.

Changed from the stock BR9EG plug to a BR8ES plug to keep it from fouling at idle.I dont know why Yamaha keep these small electode plugs as they seem to have a hard time burning the mixture correctly.

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