Question about 2003 Harley Davidson FXST Softail Standard

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2003 harley softail carb,modle where is the mixture screw and does it have a anti tamper cover do u screw in to richen or out to richen.????????

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If your bike is still equipped with the stock Keihen CV carb, there is an IDLE mxture screw but it is covered with an anti-tamper plug unless someone has removed it. If the anti-tamper plug has been removed, you turn the screw inward to lean the IDLE mixture, outward to richen the IDLE mixture. This screw only changes the IDLE mixture and has very little effect on the slow or high speed mixture. This mixture is controlled by jets inside the carb.

You didn't tell me why you wanted to know this information. If you are having a problem with the carb idling either too rich or too lean, you probably have something wrong with the carb that a simple turn of a screw is not going to remedy. The Keihen CV is a good carb and functions well when everything is right. I'm still running one on my 1994 FXDWG with over 30K miles on it and never has minute's trouble with it. If you're having a problem tell me what it is and maybe there's a simple solution for it.

Good Luck

Posted on Aug 23, 2010

Testimonial: "Hi the reason i thought about idal mix is that like many Harley riders mine backfires on the over run it was like poping but since i drilled out the b"

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Is a 1998 95th anniversary harley davidson softail springer have a carburator

Hi Anonymous, on the right hand side of the carburator there is an idle adjusting screw with a spring behind it, turn screw clockwise to increase idle counter clockwise to decrease idle. There is also an air/fuel mixture screw inside a carb body lug that may or may not be plugged with an aluminum cap that's about 3/16" thick. This cap can be drilled out to acess the air/fuel mixture screw. Turning screw clockwise will lean out mixture and lower idle, turning screw counter clockwise will richen mixture and raise idle. You need to balance the two adjusting screws to obtain an idle of 950-1000 RPM then back out air/fuel mixture screw 1/4 turn, snap throttle to confirm responce, you may continue to back out air/fuel mixture screw untill desired throttle responce is achieved, if you see black smoke coming out of exhaust you have gone to far and need to turn screw back in 1/8 turn at a time, final adjustment should be made with the engine at normal operating temperature. Good luck and hace nice day.

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If your bike is equipped with the original Keihen CV carb, you should not be able to adjust the idle mixture as the mixture adjustment screw was covered by an "anti-tamper" plug from the factory. If someone has drilled this out, there has probably been some other modifications made as well. The initial setting for this carb is about 3 1/4 turn off the bottom.

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Apr 17, 2011 | 2000 Harley Davidson FXDWG Dyna Wide Glide

1 Answer

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The idle mixture screw is on the bottom of the carb behind the float bowl. Unless it has been modified, this screw is covered by an "anti-tamper" plug and you cannot get to it to make an adjustment. If you wish to make it adjustable. You'l have to take the carb off the engine, turn it upside down and drill out the anti-tamper plug. Be very careful doing this or you'll destroy the screw underneath the plug.

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1 Answer

It starts fine i have to pull the "choke" out and leave it out. when it warms up and i should be able to push the "choke" in it wil dir every time. i had valve seals replaced last year....

Well, you didn't say what model bike it is but it sounds like the typical cold natured Harley. They will not idle properly until they're completely up to operating temp and this usually takes 3-5 miles riding to get there. This is caused by the lean mixture of the carb as demanded by the EPA. Now, You can drop the float bowl and go up one size on the slow jet and this will help but you need to know what you're doing when you get inside of the carb. It probably has a #42 slow jet in it. Got to a #45 and put a 0.020" shim under the needle in the carb to richen up the midrange mixture just a tad. You'll need to drill out the "anti-tamper" plug that covers the idle mixture adjuster screw and reset the idle mixture to the best idle.

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1 Answer

What is the correct fuel mixture for a harley davidson softtail 2001

The correct fuel air mixture for your softail is 13.5:1 - 14:1. If you stay closer to the 13.5:1 end of the range, the engine will run cooler. The carb's stock slow speed jet is a number #45. You can go to a #48 or #50 and get a better idle. Don't change the main jet. Carefully drill out the anti-tamper plug that covers the idle mixture adjustment screw just behind the float bowl and adjust for the highest smoothest idle.

Good Luck

Feb 14, 2011 | 2001 Harley Davidson FXST Softail Standard

1 Answer

I have a 2003 FXD Superglide with low backfires, hestitates and seems to run lean..It runs just fine when I pull out the maunal choke slightly...Is it a carburetor problem or an air mixture...

Your carb probably need going through. I would suspect that it's your accelerator pump has got a few holes in the diaphragm and maybe your slow jet is partially stopped up. If the bike has been sitting for an extended period of time, this is more likely the problem. The air mixture is not adjustable unless you or someone else has removed the "anti-tamper plug" that covers the idle mixture adjustment screw. And, only then if you or someone else has turned the screw. If the fuel air mixture has changed, it's something wrong inside the carb. I'd either take it apart and clean it or get someone else with the proper experience to do it for me.

Good Luck

Oct 22, 2010 | 2003 Harley Davidson FXD Dyna Super Glide

1 Answer

Carb is popping and running lean

Usually, if you go up one size on the slow jet and readjust the idle mixture this solves the problem. I think you bike came equipped with a #42 slow jet. Go up to a #45, the next step richer. If you have not drilled and removed the "anti-tamper plug" that covers the idle mixture adjusting screw, do so. Be careful not to damage the screw as they are not available seperately from Harley. This will enrichen the low speed mixture just a bit.

You can also remove the needle from the slide and install a 3 mm flat washer that is about 0.020" thick on the needle to raise it up just a bit to enrichen the midrange just a bit.

Also, check your accelerator pump for proper operation.

Good Luck

Jul 03, 2010 | 2003 Harley Davidson XLH 883 Sportster

1 Answer

2003 heritage softail spits and coughts ---sometimes

Sounds like the typical lean mixture problem. They are jetted very lean from the factory in order to meet EPA emission standards. This results in spitting back out of the carb and stumbling on take off and idle. You need to richen the carburator a bit. To do this requires some disassembly of the carb. If you're not comfortable with doing this, take it someone who is.

To richen the mixture you can buy a "Dyna Jet Kit" to do the job with or you can simply buy the jet you're going to need. I prefer buying the jet, it's much less expensive. You'll need a #48 or #50 slow speed jet, a 3 millimeter flat washer, and a new carburator spigot seal.

Remove the carb from the engine. Remove the float bowl and replace the slow speed jet with either of the new jets. Your carb should have a #45 slow jet in it if it is the factory jet. Replace it with the #48. If it already has a #48, go with the #50. Replace the float bowl on the carburator.

Remove the top cover from the carburator where the diagraphm is. There is a large but relatively weak spring under this cover. Carefully remove the diagraphm and the slide. Look down into the slide and you'll see a plastic needle retainer. Lift this out by pushing up on the needle and taking the plastic piece out. Remove the needle. You'll see a metal band around the top end of the needle. Starting from the pointed end of the needle, slide the 3mm washer up to this band. A small dab of grease will hold the washer in position while you reassemble the needle into the slide. The purpose of the washer is to RAISE the needle about 0.020" thereby richening the midrange fuel mixture slightly. Make sure the washer is UNDER the metal band when the needle is back in the slide. Reassembly is reverse of the disassembly. Be VERY CAREFUL when reinstalling the slide/diagraphm assembly, Do not pinch the diagraphm. If you pinch a hole in it, the assembly must be replaced. Cost about $100. Make sure you get the edge of the diagraphm into the groove all the way around at the top before putting the spring and top cover back on.

Now, turn the carb upside down and find the "anti-tamper" plug on the carb idle mixture adjustment screw. It's an aluminum plug that covers the idle mixture screw. It's on the backside of the float bowl towards the engine. Take a small drill bit and carefully drill through this plug. Do not drill too deeply or you will damage the idle mixture screw. Once you have the small hole drilled, start a sheet metal screw into the hole and use a pair of pliers to pull the plug out. You now have access to the idle mixture adjuster screw.

Reinstall the carb back on the engine and check for proper operation. Make sure the throttle works properly. Start the engine and allow it to warm up. Adjust the idle mixture screw for highest and smoothest idle RPM. It should be a little over 3 turns out from the "bottom". To find the "bottom", with the engine off, carefully turn the screw inward until it stops. Do not force the screw, just until it "bottoms out". Then come back out about three turns and adjust from there for best idle. Set the engine idle speed at 1000 RPM using the throttle stop screw.

This sounds like a difficult job but it really isn't. But, if you're not comfortable with disassembling the carb, best take it to someone who is. The biggest thing is DO NOT PINCH A HOLE IN THE DIAGRAPHM.
Good luck!!!

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1 Answer

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Unless the "anti-tamper plug" has been removed that covers the idle mixture screw, you cannot adjust the carb. If the plug has been removed, you adjust the carb exactly like you would any other carb, for the highest, smoothest idle speed. Once this is obtained, adjust the idle stop screw to obtain the correct idle speed of 1000-1100 RPM.

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