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Everything Dirt Bike
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Honda
Bringing back a Crf230l
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<blockquote data-quote="SRAD97750" data-source="post: 131016" data-attributes="member: 425"><p>What you describe is a "hanging idle." Typically caused by a cracked airboot downstream of the carburetor, which makes it impossible to fix by adjusting the carburetor. But since yours is nice and clean, I am fairly positive the airbox modification is the culprit. </p><p> </p><p>OK. Since we're "going there," I'll whip it out all over you...</p><p> </p><p>There are multiple 'circuits' (passages) in the carburetor that are metered by jets. Each circuit reacts differently at different <u>throttle positions.</u> Each circuit is adjustable, some in multiple ways. </p><p>For this instance,</p><p>With the throttle closed, the idle circuit (sometimes called slow jet) provides fuel through a jet and downstream of the slide. Typically much smaller than the other jets, and has a screw adjustment on the side/bottom of the carb. This is called the idle mixture screw. It can be adjusted 'on the fly.' The jet is also interchangable and sizes come in tiny increments. Typically $3-$6 each.</p><p> </p><p>So, first and most importantly, you need to get the bike completely warmed up. So that you can't touch the cylinder with your hand. If it's not warmed up completely, you are wasting your time.</p><p>Second, let it come to idle. Turn the idle speed screw so the rpms increase to a high idle. <u>The following is performed at a high idle.</u></p><p>Next, turn the idle mixture screw slowly counter-clockwise until the engine speed slows. (Richening)</p><p>Now, Turn it clockwise until the idle speed peaks. (Leaning) Stop there, and back it out 1/8 of a turn. (Should be slightly rich for cooling)</p><p>Lastly, set your idle speed screw back down to a realistic idle speed.</p><p> </p><p>This should solve your hanging idle cause by an airbox mod. This means you will also increase the power potential of the carburetor as a whole!</p><p>To read more about this subject I strongly suggest this website. It is an excellent source on carburetor theory.</p><p><a href="http://www.iwt.com.au/mikunicarb.htm" target="_blank">http://www.iwt.com.au/mikunicarb.htm</a></p><p>DISCLAIMER: 2 stroke carburetors typically have idle mixture screws that control air intake. 4 stroke carburetors use a screw that controls fuel. </p><p> </p><p> </p><p>Now, on to your needle adjustment, which I recommend over changing the main jet.</p><p>Take a photo of your needle and slide separated, i'll explain how to adjust it. It's not like a regular carburetor slide. </p><p> </p><p><img src="https://www.dirtbikeaddicts.com/static/images/smilies/wiggle.gif" class="smilie" loading="lazy" alt=":wiggle:" title="Wiggle :wiggle:" data-shortname=":wiggle:" />-BIG DAN</p></blockquote><p></p>
[QUOTE="SRAD97750, post: 131016, member: 425"] What you describe is a "hanging idle." Typically caused by a cracked airboot downstream of the carburetor, which makes it impossible to fix by adjusting the carburetor. But since yours is nice and clean, I am fairly positive the airbox modification is the culprit. OK. Since we're "going there," I'll whip it out all over you... There are multiple 'circuits' (passages) in the carburetor that are metered by jets. Each circuit reacts differently at different [U]throttle positions.[/U] Each circuit is adjustable, some in multiple ways. For this instance, With the throttle closed, the idle circuit (sometimes called slow jet) provides fuel through a jet and downstream of the slide. Typically much smaller than the other jets, and has a screw adjustment on the side/bottom of the carb. This is called the idle mixture screw. It can be adjusted 'on the fly.' The jet is also interchangable and sizes come in tiny increments. Typically $3-$6 each. So, first and most importantly, you need to get the bike completely warmed up. So that you can't touch the cylinder with your hand. If it's not warmed up completely, you are wasting your time. Second, let it come to idle. Turn the idle speed screw so the rpms increase to a high idle. [U]The following is performed at a high idle.[/U] Next, turn the idle mixture screw slowly counter-clockwise until the engine speed slows. (Richening) Now, Turn it clockwise until the idle speed peaks. (Leaning) Stop there, and back it out 1/8 of a turn. (Should be slightly rich for cooling) Lastly, set your idle speed screw back down to a realistic idle speed. This should solve your hanging idle cause by an airbox mod. This means you will also increase the power potential of the carburetor as a whole! To read more about this subject I strongly suggest this website. It is an excellent source on carburetor theory. [URL]http://www.iwt.com.au/mikunicarb.htm[/URL] DISCLAIMER: 2 stroke carburetors typically have idle mixture screws that control air intake. 4 stroke carburetors use a screw that controls fuel. Now, on to your needle adjustment, which I recommend over changing the main jet. Take a photo of your needle and slide separated, i'll explain how to adjust it. It's not like a regular carburetor slide. :wiggle:-BIG DAN [/QUOTE]
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Bringing back a Crf230l
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