Question about 2004 Harley Davidson XL 1200 C Sportster Custom

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2004 XL 1200 C won't pass emmisions, CO too high. Idle mixture screw seems ineffective. cleaned the plugs, turned the mixture screw in a complete turn and got the same numbers back on the second test. It does smell rich while idling, so i tried turning the idle screw in while the bike was warmed up and running, and was able to bottom out the screw without killing the motor, that doesn't seem right.

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No this is not right. I would see what size your pilot jet is , drop a number and try again. Less than one and a half turns out on the adjustment screw usually means your pilot jet is too large

Posted on Jul 14, 2009


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Dec 26, 2013 | 2005 Harley Davidson XL 1200 C Sportster...

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Hi, Anonymous "WEAKENS" it should be noted that the "AIR FUEL" mixture screw adjustment "ONLY" manages your idle and has no effect on any other circuit also any intake leaks must be repaired before the A/F adjustment procedure can be performed otherwise you will never obtain a proper idle and you will waste a lot of time chasing the impossible. The A/F mixture screw's purpose is to fine tune the fuel charge entering the combustion chamber. The following applies to both 2 and 4 stroke engines:
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1 Answer

Backfires at low rpms check engine light and owners manuel says ignition problem

As I understand it, your engine is spitting back out the carburetor when idling and runs poorly at low RPM.

This is probably because the engine is jetted way too lean. Now the newer model bikes have all sorts of computer stuff on them. I don't have a lot of experience on these but this is what we'd do on a 1999 or earlier model.

The low speed jet in your carb is probably a #42 jet. I'd got up to the next size, a #45 jet. I'd take the top off the carb and lift the slide out. Once I got the slide out, remove the needle. Put a 0.020" thick washer on the bottom side of the needle. I have found that a 3mm flat washer is the perfect thing to use. Slide the washer on from the lower tip of the needle and use a small dab of grease to hold the washer until it you get it back in the slide. Now, there is an anti-tamper plug over the idle mixture screw. You must drill a hole in the plug just deep enough to go through the plug. Use a tap to tap into the plug and force it out. Beneath the plug you'll see the idle mixture screw, turn it inwards until it lightly seats, the back it out 3 1/2 turns. Reassemble the carb, start the engine, and adjust the idle mixture screw for best idle. Set idle speed at 1000-1200 RPM.

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