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Jetting jetting jetting???

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You know honestly I have always neglected jetting on my bikes and just rode the piss out of them and thought that I would burn everything off. Well its time for me to get serious about this jetting deal. I got a 03' YZ250 and I couldnt tell you where the pilot or main or needle is....I read the FAQ jetting deal and the float bowl deal is somewhat understandble for me. Is there a website that has a picture of a carb already on a bike thats turned sideways with the flaot bowl off and arrows pointing to the jets labeled each one? Thats what I need. I get confused really easily with exploded views diagrams. Help would be appreciated. I hate working on carbs but I gotta do it if i want the most from my bike. :thumbsup:

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I've got an 03 too... I don't have pics, but it's pretty simple, so I'll try to explain it. Turn the gas off (obviously). To turn the carb I find it's easiest to disassemble the throttle, so i can get some more slack in the cable. For the needle, working from the left side of the bike, turn the carb so the top is facing you (this is really easy with the tank off, but it's not necessary). Use some compressed air to blast off any dirt, then remove the two screws holding the top of the carb on. With those out, you'll be able to gently lift up and the cap will lift off with the spring and slide. Now before you pull it out, note the little lever with the wheel on it that rides on the top of the slide, this is for the TPS. Lift the lever up so you can clear the way to lift the slide out. Remember to reinstall this the same way later. So the slide is in your hand, attached to the cable still, the cable is retained by the plastic ring that supports the spring. So pull the spring back and if the plastic doesn't come with it, hold the slide upside down and shake it out (note the protuding notch on the retainer, this must go back into the cable slot. So you're holding the spring back, the cable gets pushed in and towards the slot on the needle retainer, this will release it. The needle and clip is hanging out right under that retainer. Just unscrew it and it'll drop right out. (BTW the N3EW needle works nicely in these bikes). Reassembly is the opposite, just take care to not get dirt in the carb, and I like to clean the slide off with some premix before dropping it back in.

So on to the main and the pilot. Rotate the carb the other way. Use a 17mm wrench to remove the plug on the fuel bowl. Look up inside there, you'll see two brass jets, one is a 6mm hex (main jet), the other is recessed into a hole in front of the main (pilot jet), this one gets removed with a small flat blade screwdriver. When reinstalling these, go easy, they don't need much torque at all. I tighten them with two fingers only.

Good luck, and don't forget to look at the jetting database. That should give you an idea of where you should start for jetting specs.

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Thank you. If anyone comes up with pics they'll still be appreciated. How do I tell if the needle is an N3EW or not? As far as adjusting the clip position, i just remove the circlip and put it where? do they count postions from the top of the needle(pointy part) or bottom?

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The N3EW will be stamped into the needle.

As far as clip position goes, the top clip will drop the needle farther down making the bike leaner, the bottom clip will raise the needle up making it richer. As far as counting, it is normally done from the top clip.

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Thank you. If anyone comes up with pics they'll still be appreciated. How do I tell if the needle is an N3EW or not? As far as adjusting the clip position, i just remove the circlip and put it where? do they count postions from the top of the needle(pointy part) or bottom?

The top of the needle is the end with the clip grooves. Standard setting is #2 notch, so it's the second groove down on the wide end. If you're at high altitude you may need leaner, like the first notch. I run mine on the second notch, but it's getting cold here, if I ride again this year I'll go to the 3rd notch.

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