Honda CRF230F - Carburetor Notes

October 12, 2014 version

 Introduction   Modifications   Big Bore   DIY Notes   Carb Notes   A look back 

On this page, I show a few pictures and give a few hints on how to work on the carburetor.
If you find any errors or would like to suggest changes, please let me know. My e-ddress is on my home page.
Click on
small pictures to see bigger versions.   You may want to print this web page for easy reference.

There are five sections:
    Changing the main jet
    Changing the needle and/or adjusting the needle clip
    Installing an extended fuel screw
    Cleaning the carb
    Detailed carb pictures


Changing the main jet

You can change the main jet without removing the carburetor from the motorcycle.

Tools you'll need

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1/4" drive ratchet, short extension, 6mm and maybe 7mm sockets
17mm open/box wrench
Medium blade screwdriver

Drain the carb

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Use the screwdriver to loosen the drain screw near the bottom of the carb float bowl. When fuel comes out of the drain hose, catch it in a small container. Retighten the screw.

Remove the bottom plug

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Use the open/box wrench to loosen the cap on the bottom of the carb float bowl. Use a rag to sop up any fuel as it dribbles out. Don't let any fuel reach the engine or pipe if they are hot from recent running.

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Unscrew the cap with your hands, being careful not to spill the fuel in the cap.

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Inspect the fuel to see if there is any water or debris. Dump the fuel into a small container and dispose of properly.

Remove the main jet

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Connect the 6mm socket to the 1/4" ratchet. Use the ratchet to loosen the main jet. You may have to push the bottom of the carb body around a bit to get the socket to seat on the main jet. You don't want the ratchet or socket hitting or dragging against anything. You also may have to loosen the carb band screws to wiggle the carb body around or tilt the carb slightly until you get a clean connection.

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After the main jet is loose, remove it completely using your fingers.

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Try not to drop it in the dirt. Look through the hole in the main jet to see if it is clean. If the hole is obscured, wait a few minutes for the fuel to evaporate, then check again. It's always a good idea to check the condition of jets as you remove them to see if any irregularities could have been contributing to a problem.


 

If the main jet comes out attached to a long brass part, don't panic. The long brass part is the needle jet holder. Disconnect the main jet from the needle jet holder using a small crescent wrench and a 6mm socket connected to the 1/4" ratchet.

Connect a 7mm socket to the short extension. Using your fingers, use the socket/extension to screw the needle jet holder back into the bottom of the carb until it's snug. Then connect the short extension to the 1/4" ratchet. Use the ratchet to tighten the needle jet holder. Do not over tighten; snug and a bit more is good.

Install the new main jet

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Verify that you have the correct main jet by checking the number embossed on the new main jet. Look through the hole in the new main jet to make sure there is no debris blocking it. Make sure the main jet is clean, and the threads are in good shape.

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Connect the 6mm socket to the short extension. Using your fingers, use the socket/extension to screw the main jet until it's snug.

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Connect the 6mm socket to the 1/4" ratchet. Use the ratchet to tighten the main jet. Do not over tighten; snug is good. You may have to push the bottom of the carb body around a bit to get the socket to seat on the main jet. You don't want the ratchet or socket hitting or dragging against anything so that you can judge the tightness of the fit and not over tighten. You also may have to loosen the carb band screws to wiggle the carb body around or tilt the carb slightly until you get a clean connection. Be patient; this is the most important part.

Reinstall the bottom cap

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Screw the bottom cap in by hand.

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Tighten the bottom cap using the 17mm open/box wrench. Don't over-tighten.

Turn the fuel petcock on and check for leaks. Ride.


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Changing the needle and/or adjusting the needle clip

You can change the needle and/or adjust the needle clip without removing the carburetor from the motorcycle. You may have to remove the seat and gas tank. You must be able to get to the top of the carb and remove parts through it. If you can tilt the carb body out from below the gas tank enough to see the entire top of the carb, then you're set. If you are using the stock throttle cable setup with both a pull and push cable, then tilting the carb becomes very difficult because the cables are in the way. If this is the case, remove the seat and tank and begin work. If you are using a non-stock throttle cable setup, such as only one pull cable, then you can remove the single cable and tilt the carb.


 

Tools you'll need

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Medium blade screwdriver
Phillips #2 screwdriver
Phillips #1 screwdriver
10mm open/box wrench - two
Special tool or wire hook or small needle nose pliers

Note about the special tool:

The special tool used for this work is an SW-10 Swinger Hook made by Ullman Devices Corp, Ridgefield, Conn. You may be able to find the tool at your local hardware store. If not, try the web. I ordered several of these tools in 2001 from Kipper Tool for about $5 each (shipping extra). If you can't locate the tool, make a wire hook from number 14 or 16 bare copper wire or similar. A small pair of needle nose pliers will also work.

2013 update - Amazon sells the SW-10 Swinger Hook for about $7.

Tilt the carb (if you can't tilt the carb, remove the seat and tank instead; see the note above)

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View of the single-pull throttle cable

Use the two 10mm box/open wrenches to loosen the lower nut. Hold the cable housing with one wrench, while you turn the lower nut with the other wrench. Slip the cable out of guide and move it behind the guide, out of the way.

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Loosen the rear band screw using the Phillips #2 screwdriver.

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Loosen the front band screw using the Phillips #2 screwdriver. Tilt the carb out so you can see the entire top.

Remove the top of the carb

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Remove the screws from the top of the carb using the Phillips #2 screwdriver.

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Peek inside.

Remove the retaining spring and link

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Remove the link arm locking screw using either Phillips screwdriver. I like to use the #1.

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Raise the slide using the Swinger or wire hook.

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Grasp the link and use the Swinger, wire hook, or small needle nose pliers to remove the retaining spring.

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Slide the link sideways off of the link arm and the slide arm. Rotate the link arm up and out of the way.

Remove the slide

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Raise the slide using the Swinger or wire hook.

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Removed parts:
Slide, link, spring, screws, top

Remove the needle

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Unscrew the small screws inside the slide using the Phillips #1 screwdriver. Be careful when removing the screws because the needle retainer has a spring under it, and it will rise up as you unscrew the screws. Remove the retainer, then tip the slide over to remove the needle.

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The needle retainer with screws and spring.


NOTE -- I read about an alternate method of removing the needle that reduces the possibility of bending the needle. Using my method described above requires that you hold the slide in one hand while you loosen and unscrew the small screws in the bottom. The screws are often seated very tightly and require significant force while rotating the screwdriver and solid seating of the tip into the screw head. During this process, the cheek of your hand could roll over the edge of the slide and push against the needle, bending it. You may not even notice it, especially if you have large hands as I do.

The alternate method is to loosen the screws while the slide is still inside the carb body. There is no possibility of bending the needle with this method. The only problem is, it's difficult to do this with the carb still in the carb boots and rotated. You must steady the carb while you break the screws loose and that's easiest with the carb removed from the boots and in your hand. At least for me. If you can do it with the carb in place, go for it. Otherwise, pop the carb out of the boots.

After you change the clip position (described below), install the slide into the carb body before re-installing the screws. Don't over-tighten the screws - you may have to adjust the clip position again. I tighten to snug and a bit more. The lock washers should be an insurance against under-tightening.

Adjust the clip

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Remove the clip from the needle. I use my fingers instead of tools. Hold the clip/needle against a hard surface with the open end of the clip pointing down. Cover the clip with a finger from one hand and press the needle down with a finger from the other hand. Press firmly, and the clip will slide off the top of the needle. Be careful the clip doesn't go flying off. Maybe you should do this in a place where you could spot the clip if it pops out of your hands ;-)

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Place the clip in its new location and press it back onto the needle. Again, I use fingers from both hands and work against a hard surface. Face the open end of the clip pointing up with the needle on top. Press down on the needle, and the clip will pop into place. Rotate the clip on the needle to make sure it's in the groove properly.

Caution: if you use pliers to remove and replace the clip, you may crimp the clip enough so that it doesn't fit properly on the needle or completely into the needle groove.

Reinstall the needle

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Drop the needle back into the slide and put the retainer, with the spring, over it, aligning the holes in the retainer with the holes in the slide. Make sure the spring is on the needle, pressing down on the clip. The retainer arm must be aligned to point to the right of the slide (the top slide cutout is to the rear).

Screw in the small screws using the Phillips #1 screwdriver. Don't over tighten because you may have to remove them some time in the future; snug and a bit more is good.

Reinstall the slide

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Put the slide back into the carb, aligning the top cutout to the rear. Don't drop it in; slide it in slowly until it bottoms.

Reinstall the link and retaining spring

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Place the link onto the slide arm and the link arm.

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Install the spring within the link. Check that the slide goes up and down by raising and lowering the link arm.

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Make sure that the link is pushed all the way to the left on the slide arm. The spring must seat in a groove on the slide arm. This picture shows an INCORRECT position of the link.

Reconnect the link arm

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Screw in the link arm locking screw; don't forget the lock washer. Don't over tighten; the lock washer works. I use the Phillips #1 screwdriver, but either will work.

To help line up the holes for the screw, do two things:

1. Push the throttle drum to the right, towards the carb body. This gets the inner shaft into the correct position. (The throttle drum is the round metal plate on the left that the throttle cables are connected to.)

2. Raise the link arm just a bit. This rotates the outer shaft so the holes in both shafts line up.

Look into the screw hole as you do this to see which action aligns the holes best. You can even do both actions at once and when the holes line up, slip the screw into place.

After the screw is tightened, rotate the throttle drum to check that the link arm and slide operate correctly.

Reinstall the top of the carb

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Replace the carb top and screw in the two screws using the Phillips #2 screwdriver.

Realign the carb

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Rotate the carb to vertical and make sure that the tab on the front of the carb is aligned with the rubber alignment slot on the intake boot. Tighten the front and rear band screws.

 

If the throttle cable was removed, use the two 10mm box/open wrenches to reinstall it.

Operate the throttle to make sure that everything works. You should hear a small clunk when the slide hits the bottom of the carb as you roll-off the throttle. Reinstall the tank and seat if they were removed and go riding.


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Installing an extended fuel screw

To install an extended fuel screw, you must remove the carburetor from the intake boot and airbox boot, so you can get to the lower front of the carb. You may be able to remove the carb without removing the seat and gas tank, but it's very difficult. I recommend that you remove the seat and tank first.

Note: Although I, and many others, call this part a fuel screw, Honda calls it a pilot screw. We use the term fuel screw to distinguish between this part for four strokes and the 2-stroke version, called an air screw. This is done so we can be ever mindful that screwing the "fuel" screw in and out adjusts the amount of "fuel" we are adding to the mix; 'in' is leaner (less fuel), and 'out' is richer (more fuel).


 

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There are three fuel screws that this section is concerned with:

the stock Honda '03-'05 fuel screw (left),
the stock Honda '06 and up fuel screw (center),
and the Kouba extended fuel screw (right).

The head of the shorter '06-and-up fuel screw is recessed in the carb body and is difficult to get to when you want to adjust the fuel screw. Honda has put these shorter D-bit-head fuel screws on many CRF models to comply with CARB, the CA agency that sets emission standards for CA motor vehicles. On some other carb models, the fuel screw chamber has a metal cap that is pressed in to cover the fuel screw and prevent adjustment.

By installing an extended fuel screw, you make it easy to adjust the fuel screw by hand. Small tweaks to compensate for temperature swings are easily done using your finger on the T.

You can buy the Kouba extended fuel screw from:
KoubaLink PN FS-3: $20 (min. order of $25 - domestic shipping included);
CRFsOnly about $20, shipping extra.


 

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If you have an '03, '04, or '05 230F, use a small screwdriver to unscrew the stock fuel screw.

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If you have an '06 or newer 230F, the head of the fuel screw is D shaped, and a regular screwdriver will not work. You can use a D bit (sold by Motion Pro for about $2.90 plus shipping).

You'll also need a driver for the bit: it's a 1/4" hex drive. I used a short 1/4" hex socket and a manual drive handle.

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If you don't want to buy the D bit, you can try using a small jeweler's screw driver to fit in along the flat edge of the D and try to rotate the stock fuel screw out. A dental pick may also be used. DO NOT drill out the stock fuel screw; you may ruin the carb.

 

The 2013 and 2014 model carbs have a brass cover over the fuel screw. You can try to remove it with a pair of needle-nose vise-grips or other tool. Another choice is to drill a small hole in it, then thread a screw in, then pull on the screw to remove the cover. You could also put a very small hook in the hole and pull; use the Swinger hook if you have it. If you have an after-market extended fuel screw that you will be installing, you don't have to worry too much about damaging the stock fuel screw hiding under the cap.

Caution - don't put any pressure on the fuel screw chamber itself; the cast material is not strong and the chamber can be broken off. Honda does not sell individual carb body parts - if you break the chamber off, you have to buy a whole new carb!

See Changing the needle and/or adjusting the needle clip for a description of the Swinger hook.

 

Tools you'll need

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Medium blade screwdriver
Small blade screwdriver
Phillips #2 screwdriver
D bit, hex socket, driver

Drain the carb

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Use the screwdriver to loosen the drain screw near the bottom of the carb float bowl. When fuel comes out of the drain hose, catch it in a small container. Retighten the screw.

Remove the carb from the intake boot and airbox boot.

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Remove the end of the upper rubber vent hose from the retaining tab on the upper frame backbone tube.

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Remove the end of the lower rubber drain hose from the retaining tab on the frame under the swingarm and behind the rear brake pedal.

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Loosen the rear band screw using the Phillips screwdriver.

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Loosen the front band screw using the Phillips screwdriver.

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Pull the front of the carb out of the intake manifold boot.

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Pull the rear of the carb out of the airbox boot.

Remove the stock fuel screw.

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Using the small screwdriver ('03-'05) or the D bit and driver ('06 and up), screw the stock fuel screw in until it bottoms lightly, counting the number of turns of the screw. Try to get 1/4 or 1/8 turn accuracy. Write this number down. It should be from 1/2 to 2 1/2 turns, but, in some cases, it may be more or less than this.

If you have an '06 and up 230F and don't have the D bit and are using some other tool, this will be difficult to do. You can bypass this step, but then you will have to do the "hot" adjustment described below.

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Using the small screwdriver ('03-'05) or the D bit and driver ('06 and up), unscrew the stock fuel screw all the way out, being careful to look for the spring, small washer, and tiny o-ring.

In this picture, we are using a toothpick to dislodge the washer and o-ring that remained in the carb after the stock fuel screw was removed.

Install the extended fuel screw.

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Do a trial fit of the new extended fuel screw only without the spring, washer, and o-ring. Grease the fuel screw threads very lightly so it will screw easily. Put it in the fuel screw chamber and slide it all the way in using your fingers. When the threads touch, screw it in a few turns using your fingers to get a feel for the action and resistance (minimal). Then, remove the screw.

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Lightly grease the o-ring so it's shiny, but no more. This will allow it to seat without causing it to roll up or stick in the chamber.

Install the spring, small washer, and tiny o-ring on the extended fuel screw.

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With the carb slightly tilted from vertical, carefully guide the fuel screw and three small parts into the fuel screw chamber and slide it all the way in using your fingers. When the threads touch, screw it in a few turns using your fingers.

Using your fingers, screw the fuel screw in until it bottoms lightly.

Then, unscrew the extended fuel screw the same number of turns that the stock fuel screw was set at. This is the number you were supposed to write down in the step where you removed the stock fuel screw. If you don't have this number, set the fuel screw to 1 1/2 turns out and do the "hot" adjustment described below.

Reinstall the carb.

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Insert the back of the carb into the airbox boot. Insert the front of the carb into the intake manifold boot. Make sure the throttle cables don't get kinked or pinched.

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Rotate the carb to vertical and make sure that the tab on the front of the carb is aligned with the rubber alignment slot on the intake boot. Tighten the front and rear band screws.

Put the ends of the vent hose and drain hose into their respective frame tabs.

Operate the throttle to make sure that everything works. You should hear a small clunk when the slide hits the bottom of the carb as you roll-off the throttle.

Reinstall the tank and seat if they were removed and go riding.

 

Hot-adjust the extended fuel screw.

Start the engine and let it warm up for a few minutes. Ride the bike a few hundred yards to ensure that the engine is warm.

Using your fingers, screw the extended fuel screw in until the engine stumbles. If you bottom the fuel screw, and there is no stumble, the pilot jet is too rich; install one size leaner pilot jet and start over.

Now, turn the fuel screw out until the engine runs the smoothest and highest rpm. You may have to hunt back and forth to find the sweet spot. Turn 1/8 turn at a time and let the engine run for 30-60 seconds to settle in at the new jetting. Once you find the sweet spot, stop the engine. If you unscrewed more than 2 1/2 turns, the pilot jet is too lean; install one size richer pilot jet and start over.

With the engine off, screw the fuel screw in until it bottoms lightly, counting the number of turns of the screw. Try to get 1/4 or 1/8 turn accuracy. Write this number down. It should be from 1/2 to 2 1/2 turns, but in some cases it may be more or less than this. Unscrew the fuel screw the number of turns you wrote down. Go riding.


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Cleaning the carb

Refer to Changing the needle and/or adjusting the needle clip above and Detailed carb pictures below to see pictures of the carb internals. The Honda CRF230F Service Manual shows more pictures and is a great help when doing this procedure. The hardest part in the whole job is unscrewing the carb screws, with the slide screws being the hardest. Buy a set of JIS screwdrivers or you'll ruin a lot of screw heads.

Remove the carb from the bike.
Remove the two screws from the top of the carb and remove the carb top.
Remove the small retaining spring and link from the link arm and slide arm.
Remove the slide screws.
Remove the link arm locking screw.
Remove the slide from the carb.
Remove the needle retainer (plus screws) and carefully remove the needle.
Remove the drain bolt on the bottom of the float bowl.
Remove the three screws from the float bowl and then the float bowl.
Remove the plastic baffle.
Remove the pin, float, and float valve.
Remove the pilot jet, main jet, and needle jet holder.
Remove the fuel screw, spring, washer, and o-ring.
Do not remove the air cut-off cover.
Do not remove the air jets in the back of the carb bell.
Clean the carb body and all internal passages.
I use carb cleaner or solvent on a rag and rub/scrub using my fingers.
A tooth brush is also helpful.
Use light air pressure to blow out passages.
Clean the jets, needle, slide, etc.

Look among the parts you have for the following:

Main jet
120  sea level
110  5,000' - 6,000'
108  6,000' - 10,000'
105  above 10,000'

Pilot jet 42

Stock needle '03-'05 16012-KPS-901 marked C39A
Set the clip in the middle position (#3) on the needle.
Adjust as needed.

Aftermarket fuel screw, preferably brass, preferably Kouba.

If you don't have these parts, buy them before proceeding.
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Assemble the carb as follows:
Assemble the fuel screw parts: fuel screw, spring, washer, o-ring.
Apply a small dab of grease on the fuel screw o-ring; very small amount.
Screw in the fuel screw until it bottoms lightly, then unscrew 1 1/2 turns out; adjust as needed.
Install the pilot jet, needle jet holder, and main jet.
Install the float valve, float, and pin.
Set the float level to 12.5mm - 13mm.
Install the plastic baffle; align the cutout with the prospective float bowl overflow tube location.
Install the float bowl; three screws.
Install the drain bolt on the bottom of the float bowl.
Install the needle in the slide and cover with the needle retainer (plus screws).
Tighten the slide screws.
Install the slide into the carb.
Install the slide screws.
Install the link and small retaining spring onto the link arm and slide arm.
Install the link arm locking screw.
Install the carb top and the two screws on the top of the carb.
Install the carb on the bike.
Check that the throttle operates the slide and the slide clunks when you release the throttle.


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Detailed carb pictures

Here are some pictures showing most of the parts in and on the carburetor.
Note: these pictures CANNOT be supersized.

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Needles are marked with an alphanumeric code that you can barely read with the naked eye.

Stock needle '03-'05  16012-KPS-901  marked C39A
Stock needle '06 and up  16012-KPS-731  marked C83A
Power up needle  16012-KPS-921  marked C30FF

Needles are shown with the fat end up and the tapered tip down. Clip positions are numbered from top to bottom; 1 (top), 2, 3, 4, 5 (bottom). Clip position 1 is the leanest, 3 is usually the stock position, and 5 is the richest. The two-clip-position needle has stock (bottom) and high-altitude (top) positions only.


Jetting part numbers
ServiceHonda.com, DiscountHondaParts.com, PartsFish.com,
jetsrus.com, rockymountainatvmc.com and others.

Name Year Part description Part number
Pilot jet, stock All years JET, SLOW (#42) 99103-MT2-0420
Pilot jet All years JET, SLOW (#45) 99103-KPS-0450
Pilot jet All years JET, SLOW (#48) 99103-KAE-0480
Main jet, stock high altitude All years JET, MAIN (#98) 99113-GHB-0980
Main jet, stock All years JET, MAIN (#102) 99113-GHB-1020
Main jet, recommended
for riding over 6,000'
All years
  
JET, MAIN (#108)
  
99101-357-1080 or
99113-GHB-1080
Main jet, recommended
for riding at 5,000 - 6,000'
All years
  
JET, MAIN (#110)
  
99101-357-1100 or
99113-GHB-1100
Main jet All years JET, MAIN (#115) 99101-357-1150
Main jet All years JET, MAIN (#118) 99101-357-1180
Main jet, recommended
for riding at sea level
All years
  
JET, MAIN (#120)
  
99113-GHB-1200 or
99101-357-1200
Main jet All years JET, MAIN (#122) 99101-357-1220
Needle set  † 2003-2005 NEEDLE SET, JET 16012-KPS-901
Needle set  † 2006 and up NEEDLE SET, JET 16012-KPS-731
Fuel screw set  †† 2003-2005 SCREW SET A  ††† 16016-KCY-670
Fuel screw set  †† 2006 and up SCREW SET A 16016-KC2-764

†  Needle set includes the needle, clip, and normally unneeded needle jet (small brass piece).
†† Fuel screw set includes the fuel screw, spring, washer, and o-ring.

††† SCREW SET A:  16016-KCY-670 replaces 16016-393-700 and 16016-393-701

 

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                    Main  99101-357 series                               Pilot  N424-21 series


 

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