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Need help with YZ426 carb problem!!!

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Help! Here's the situation... Bike starts fine and purrs like a kitten when it's cold. Once it warms up, it will not idle and is very sluggish like it is really rich. Here's the thing that I can't figure out... I can screw the fuel screw ALL the way in and it still runs (actually runs slightly better)? I've tried a #40 and #42 pilot jet with no effects. This all started after I replaced the piston and rings and added the Hot Cams exhaust cam. I've checked and rechecked the valve timing and clearances and cleaned the carb twice. Anyone have any ideas as the what the problem could be??? :thumbsup:

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Thanks, I'll give that a try. One other thing, I can make it idle by turning the idle knob way in, but then it runs like crap. When I'll pulled the carb and looked in at the slide, it was 1/4" open at this setting... can't be a good thing!

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I have a 39fcrmx carb that has been hell trying to get the pilot set right.I followed eddie's advice in the sticky note but the bike runs with the fuel screw turned all the way in.

It runs best with it turned all the way in too.I have tryed pilot jets from 35 to 50 and can't seem to get it.The fuel screw is a zip ty and I'm thinking about putting the oem fuel screw back in and trying it again.

I know the nozzle (tube the main jet screws into) is not worn and the needle is good to.

Eddie,what is the "needle jet" Fuel screw/zip ty?

Thanks for any help

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I had the Zip Ty fuel screw in the bike but I took it out and put it in the new 450. Same results with the stock fuel screw. I have not had a chance to order the needle jet jet, but it is #1 on my "to do" list. Hope this will fix it cause I need to sell the beast, but I won't do that til I know everything is right with it!

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