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need help understanding jetting

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ok im new at this jetting thing, well new at motocross all together and i have no understanding of what jetting is. how do i know my bike is jetted right?!?!?! can someone help me.

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Jetting is the ART of getting the fuel/air ratio into the engine in the correct porportions. Proper jetting will help maximize the engine's power across the entire powerband.

Different circuits in the carb affect different throttle settings. For example, the pilot circuit, including the pilot jet, fuel screw and pilot air jet affect idle to about 1/4 or 3/8 throttle. From there, the needle clip position and needle profile takes over. After that, at about 5/8 to 3/4 throttle, the main jet has the most effect on up to full throttle. Also, there is quite a bit of overlap between these carb circuits.

Here's a nice link with the basics. http://www.motocross.com/motoprof/moto/mcycle/carb101/carb101.html

Read up, search the jetting forum and ask questions. That's how everyone starts out. Good luck and welcome to TT. :thumbsup:

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Research on this topic will last you a couple of decades, then you will be dangerous enough to change your jetting only to find out you still don't know what you are doing. Seriously, what you are trying to accomplish is the perfect ratio of air and gas( 14.6:1 I think.) I see you have a 2006 yz250f. I have an 03. There are 4 separate jets or circuits you will be aware of. 1st (1st 1/4 of throttle opening) which is adjusted by a screw on the bottom of your carb. If the screw doesn't adjust far enough, then you get into changing pilot jet. The screw fine tunes the pilot jet. You can get an extended screw to make it easier to adjust. Get one, they are cheap. 2nd is the needle jet, which is located in the top of your carb. It adjusts the midrange. It looks like a small knitting needle that has different grooves in the top of it so you can move a clip. Moving the clip will allow you to adjust how far down the needle will fall. 3rd is the Main jet. It is located on the bottom of your carb, and regulates the high or full throttle range. 4th is the leak jet. When you twist the throttle open very quickly (but not when you just roll on the throttle) it will cause a lean condition. The leak jet will squirt extra fuel into the engine helping the lean condition. This jet should only be adjusted if you have a problem when you twist the throttle very quickly and get a bog or stall. Research bog and you will have another decade of reading on your plate. Before you change any of your jetting, learn what your bike is doing and why. Learn how to detect a rich or lean setting, and in what part of the throttle it is in. If you are just starting, and do not have any problems with your bike, I would just do your research. If you think there is a problem, just ask specific questions, and I am sure, some body much better at jetting problems than I, can help. I hope this help you a little. I am by no means and expert, but I hope my limited knowledge explained the basics in a simple manner.

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