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Discussion Starter #1
Hi, the guy I bought my bike from mentioned something about adjustment a screw or something if I wanted to adjust the mixture to make it more rich/lean. I can't remember what he said, though, and I'm wondering if someone could direct me to pictures/more info on where to find this adjustment screw for my 2004 Honda Nighthawk 250. Thanks!
 

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Gone.
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I don't want to discourage you from working on your own scoot, but if you don't know exactly how and why to adjust your air / fuel mixture it's not something you should probably be horsing around with. The reason is that you can potentially ruin your engine, especially if you set the AFR too lean.

Why is it that you want to change the mixture? Are you certain the mixture needs adjusting, and not just the idle speed?
 

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Discussion Starter #3
Hi, thanks for the reply. I'm not sure which one I want, but the guy said if its running too lean I could adjust something. It's been taking a long time for my bike to warm up so I thought that's something I should try?
 

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Discussion Starter #5
It's about ~70 degrees but it takes about ~15 minutes to warm up. Is that normal? I know nighthawks are cold-blooded but this seems like a long time.
 

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That does seem too long, yeap.

It could be that it's running lean due to the mixture adjustment, or that it has a slightly clogged carburetor passage. It can also be a leak in the intake somewhere. What I would do next though is pull the plugs and see how they look to get an idea of if it's a lean condition or possibly some other issue.

Now, I don't work on that kind of bike so I can only give you general sort of ideas, but there are a few people here that should be able to give you more specific help soon.
 

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Ace Tuner
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Like angle said, pull the plugs to see if they are bright white/clean with no or very little deposits on them. If so, that could indicate a lean mixture.

The idle/slow speed fuel mixture screw is on the bottom of the carburetor in the center and in front of the fuel bowl.
(It's dead center of the carb bore, straight up and all the way toward the front).
It came from the factory with a 'limiter' on it. The limiter sorta looks like a little tab sticking out to the side and limits how far it can be turned.
Many times service tech's or customers will remove the limiter. Then it looks like an odd screw head.
Or the tab part could have been cut off. Then it looks like a mangled aluminum knob.

Turning the fuel mixture screw out rich-ens the mixture. (More fuel).
About 1/4 turn usually makes for a noticeable change.
 

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2007 Yamaha Road Star Silverado 1700
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I would be willing to bet that a maladjusted mixture screw is probably the LEAST common cause of a bike running lean. Far more likely there is an air leak or other carburetor problem
 
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