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Raptor carbs, float level and clear tube method explained.

I have a similar post on how to set up the carbs correctly, but I found that some people got confused and some of the pictures also got lost on the old post.

So here goes.

I will also start with the basics on how to get started.

Remove all the plastics on the front of the bike. Next remove the fuel tank and the air box. Make sure you close the fuel delivery before you remove the tank.

For those of you that would like to know what mods to do to the airbox to get it flowing correctly read on. Cut out the rubber flaps inside the snorkel. The Snorkel should have no restrictions if you look inside it. Then cut additional plastic out of the airbox lid where the air flows into the airbox. Look at the picture below to see how to cut it. It opens the air intakes a little more. Some people cut all of it out, but I left some of it behind. The theory is that if water comes into the intake, it will bypass most of the filter and the water will collect at the back of the airbox.



For more airflow you can cut two 50 mm holes into the back of the lid. This is a similar mod recommended by Yoshimura and it works well. I installed two pipes into the holes that run down ½ to 2/3 down into the airbox. This was done to help prevent water form getting onto the air cleaner. Please note that it will increase the chances of water getting into the airbox, but this mod with the pipes will keep water away from the air cleaner much more than without a lid. Then other people remove the lid completely. If you run in wet muddy conditions, run with the lid. It’s up to you how you want to modify it. YES you have to rejet with these mods. Most people also install a 25 Pilot jet to get the idle mixture right. The number of turn on the airscrew will depend on your mods. Anything from 2.5 to 3.5 turn should do the trick. Play around till you have a good setting. Now for a warning. Some people, including myself have found that with the open lid the bike will have a slight low RPM stumble. I have not been able to fix it. The problem is caused by pressure waves inside the stock rubber intakes between the carb and the airbox. This pressure wave causes the sliders inside the carbs to move erratically and it causes a slight stumble. This only happens with very small throttle openings. If you open the throttle a little more it goes away. Its not a major problem, but be aware of this.

See a picture of the additional mods below.



For those of you that need to know how to remove the needles. The picture below shows the plastic tops on the carbs removed and what you will find underneath them. Be careful when opening these lids. There is a spring underneath the lid and it will jump out of you are not careful. Do one at a time, so if you get things wrong, you always have another one as a sample.



The below picture shows how it looks like with the needles removed. TAKE note of the small little springs. They get lost very easily. I like to take the whole slider and put it upside down on a table. Needle facing upwards at you. Then softly press down with your finger on the needle, taking care not to press to hard, until it clicks. When you turn the slider back up, you will find the little spring laying there waiting for you. In the picture you will also notice two set of slider springs and needles. The ones on the left are stock, the ones on the right comes with the dynojet stage 2 kit. The Dynojet needle on the right is much sharper and has 6 different setting, compared to the thicker stock needle with 5 settings. You need the needle in the 3rd clip with the stock setup and the 4th clip with the dynojet needles. Moving the clip towards the sharp end, will enrich the fuel mixture. Moving the needle away form the sharp end will lean out the fuel mixture.



When you are done with the needles put them back the way you took them out and put the plastic caps back on the carbs.

Next remove the carbs. I did not take the throttle cable out. It is possible to work with the cables attached. Put a bowl under the carb before you turn it upside down. When you turn them around fuel will drain from the carbs. Below is a picture of the carbs upside down. You will notice a clear tube on the one carb. It will be used for checking the floats at a later stage. You need to move the clear tube between the carbs to check both float levels. Keep in mind that they will only be used when the carbs are mounted back on the motor.



Remove the float bowl. You have 4 screws on each bowl. Take note, these screws are very soft and strip very easy. Use a nice big screwdriver that fits the screw perfectly. To small and they will strip. Good advice is to get new steel screws of you can. Also take special care when you tighten them later. The picture next to it shows different coloured arrows.

The red arrows are for the fuel mixture. Turn them in until they are seated. NOT TO TIGHT. Then turn them out 3 turns. (I used the dynojet stage 2 kit settings. It might be different for other jets). You might have to do final adjustments at a later stage to get them perfect.

The Blue arrows point to the floats. More later.
The green arrows are pointing at the main jets. More later.
The yellow arrows are the Pilot jets. With the dynojet kit they don’t recommend that you change them, but I personally changed them for bigger pilots. I had to order them separately. With GYT-R, you get them with the kit.


The below picture shows one of the main jets removed. I had to replace them, because of the airbox mods I have done. Note there are 3 peaces to this “jet” Use a small spanner to keep the 3rd peace in place. You should only remove the top two peaces. Notice them lying to the left hand side of the carbs. Replace the main jet if required and put them back the way they came out. Again use the right screwdriver. To small and it will cause damage to the jet. Don’t tighten it to much.



Now to check the float levels. Please follow this exactly! To start do the following. With the float bowls removed turn the carbs upright. (the same way they are mounted on the motor) The floats are now hanging fully opened. Now slowly start turning the carbs to 90 degrees with the openings that connects to the motor facing down. Move the carbs between upright and 90 degrees and look at what the floats are doing. When the carbs are nearly at 90 degrees you will notice the floats move and suddenly pause. It will pause for a little and if you keep turning it will start moving again. You need to find where it pauses and hold it there. It is the position where the floats touch the needle valve pin. Measure between the split (place where the float bowl and carb comes together) and the little shoulder of the float. It should measure 13 mm. The image is showing you how to hold the carb in the right position to measure the floats.


Note the measurement in the picture is slightly off.

The floats on my bike were out so I had to adjust it. The level was to high. If you need to adjust the level, you need to take the floats off. There is one screw that holds it in place. Remove it and off comes the floats. A small little needle valve will be dangling on the float. Take care of it. The picture below shows it apart.



With the floats off, you will notice a small little metal thingy at the back of the floats called a tang. You need to bend it to get the right float level. Bending the tang down towards the bottom of the float will lift the float level. Bending the tang towards the top of the floats will lower the float level. Adjust it, put it back in the carb and check if it measures to 13mm. Make sure you measure it as explained above. PLEASE NOTE. The 13mm measurement is pure a guideline. See the clear tube method later in the post to make 100% sure the float level is correct.

I had another problem. After adjusting the floats to 13mm the floats would not open correctly and restrict fuel delivery. You can test to see if you have the same problem. With the floats adjusted correctly and fitted in the carbs, turn the carbs upright and hold it there (Same way as they are mounted on the motor). Now blow into the fuel pipe that connects to the fuel tank. It should flow air very easily. Make sure that both carbs are flowing. Press each float softly upwards till it stops flowing air. If you let go of the float is should flow air again. If it does not flow air, or has a restricted flow, you have a problem. You need to mod the floats. It should flow easy, but keep in mind there is only a small little hole. To be safe it will not hurt doing the float mod anyway.

The picture below shows the float level mod. Take a small little file and file down the little plastic stopper at the back of the float. DON’T shorten it. Take a 45 degree angle off it. Take note, it should look like the float below. The screwdriver is pointing at the little stopper.



After this mod it should open real easy and you should have no problem blowing thru the fuel intake pipe when the carbs are the right way up.

When this is done and the floats are set correctly, put the carbs back together. Take note not to tighten the screws to much. When the carbs are all back together and you need to putt them back, I found that I struggled with the rubber intakes on the head. To prevent it from sticking to go back in, make sure the clamp screws are loose all the way. Then dip your finger in some fuel and rub it inside the intake. With the fuel still wet, the carbs will slide in real easy.

Clear Tube Method

Now to check the float level with the carbs in place. This method will make 100% sure the float levels are right. You don’t have to tighten the clamps on the rubber intakes to check the float levels. Do that once the level is correct.
1st put the fuel tank back, again don’t worry about tightening it up. Connect the fuel intake hose from the carbs to the fuel tank and open the little tap. The fuel should now flow into the carbs. Check for leaks. If none, you check the floats using a clear tube. The size of the clear tube must just fit the little drain hole on the bottom of the carb. I showed you before where this pipe connects. The picture below shows you the clear pipe and the screwdriver is pointing to a small drain screw on the bottom of the carb. Point the clear tube up and above the section where the carb and float bowl joins. Open the drain screw and you should see fuel run into the pipe.



When the fuel stops flowing, tap the pipe a little to make sure there is no air bubbles trapped inside it. Push the pipe against the carb and the fuel level should be 3mm above split between the carb and the float bowl. When this is done close the drain screw. You will have to move the clear tube and go to both sides of the bike to check the two carbs. Don't try checking it from the same side. See picture below. PS. my finger is not pointing at the fuel level, it is only holding the pipe in place.



If it is not correct you have to bend the little tang on the float up or down to get the level right. 13mm as explained above work almost all the time, but I have had some cases where it needs to be at 14,15 or even 16mm to get the clear tube level of 3mm right.

When you are happy with the results, tighten up all the clamps, put it all back together and make sure there is no bolts and nuts left. PLEASE NOTE. When you tighten the rubber intakes onto the carb, they sometimes move and cause gaps and little air leaks. Make sure they are mounted correctly and they are not pushed open by the clamps.

Hope this explains more clearly how to get the carbs set up right and you find it useful.
 

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i have a ? about the clamps i can never get them to go on the little piece between the boots gets in the way so i had to use zip ties got any helpful hints
 

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Discussion Starter #3
Make sure that the carbs and rubber hoses are dry. If you have any oil or fuel on it, the rubber will move when you tighten up the clamps. Take care and take time when tightening them. If the rubbers start moving as you tighten them, try pushing the carbs back or forward to make sure it clamps correctly. You don’t have to tighten the clamps between the carb and airbox to much. Just tighten them up to make a good seal.

The rubbers between the carbs and head needs to be tight. It has a stopper that determines where to stop. As with everything, don’t tighten it to much.
 

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I hope this gets stickied. I get so lost when it comes to carbs. I need to do this to my raptor. I like doing the little stuff that tunes it and maximizes what is already ther. Thanks for the great post!
 

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Very helpful post. Thanks for taking the time to explain this in detail. The mods should thnk about making this a sticky :hey: :hey:
 

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Thanks for the effort and time that you put into this post. By reading this I finally got all my questions answered that I had about adjusting the carbs.

Thanks
 

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Very nice job.....already printed it out!
 

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Discussion Starter #9
Glad you guys find it useful.

fasterblasteryfz450, to drop the float level and make it have less fuel inside the carb you need to bend the tang down. If you look at the picture below, you need to bend the tang towards the screw driver. Only small changes are required. Try checking the float level by holding it at about 90 degrees and measuring it to 13mm. I explain how to do it in the main post. If it is still too high try 14, 15 or 16mm.

 

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3mm above or below ?

I am curious, you say the fuel level should be 3mm above the carb/float bowl split. My shop manual says 3mm below the split ?
 

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Discussion Starter #11
The manual is wrong. I struggled for weeks to get it set according to the manual, but it is impossible. The lowest I cold get my float levels was just under the split. The float bowl prevents the floats from getting much lower. You also will find that if you run the floats level with the split, the amount of fuel inside the carb can create a problem. The low level of fuel will be sucked up very quickly by the motor and the floats will almost always be in an open condition. Since the float bowl is restricting the amount the floats can open, very little fuel gets supplied to the carbs. Running at WOT can cause the fuel to be sucked up at a higher rate as what the restricted float opening can provide. This can cause very lean conditions at WOT and it is extremely bad for the motor. Some people even complain that the motor suck the carbs dry when you going up a small hill with the floats set to be level with the split.

On 686 or bigger bore raptors the fuel delivery becomes a much bigger problem. Most guys have to install bigger needle valves and seats and also mod the carbs to flow more fuel to prevent the float bowls from getting to little fuel.

Setting the fuel level to 3mm above the split, will help the floats to open the needle valves more and flow much more fuel. The float mod I have shown you above helps the floats to deliver the biggest possible opening and this ensures faster fuel delivery. I also found that setting the fuel level to 3mm causes the motor to respond very well. Other people that have done these mods correctly all came back and said the bike had more power and much better throttle response.

The manual says to adjust the float height to 13mm. I agree with the manual on that one. When you have done that correctly, the float level is at 3mm ABOVE the split. Not all floats are made exactly the same and you might have to move them a little. Some might have to be set to 14, 15 or even 16 mm to get the float level right at 3mm.
 

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One more Question ?

Now with the fuel level higher in the carb bowl , you must dump some fuel when wheeling correct ? I checked mine this morning and my were way off, i'm sure that is what is wrong when WOT, i am getting a backfire then it wants to quit. My floats were way out. I notice in the online manual it says nothing about not compressing the needle valve when measuring, but in my manual it has a note saying not to compress when measuring, that would probably account for the 3mm. I'll let you know how it turns out.
 

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Discussion Starter #13
You might spill some fuel when you wheelie, but the bike will run great. I personally don't see that as a problem. I rather waist a little fuel once in a while when I am on the back wheels and have great performance in return.

Yes, the manual say you must not compress the needle valve spring when you measure the float height. That’s why I say you have to measure the 13mm with the carbs at around 90 degrees and looking for the "pause" in movement. At that angel the floats will stop and pause when they touch the needle valve. If you turn it further the floats will start moving again, meaning they are not compressing the needle valve. It a lot easier to measure the 13mm at that angle cause you can use one hand to hold the carb and the other to hold the ruler. If you do it with the carbs upside down you will have to do some fancy tricks to keep the floats in place and not compressing the needle valves.
 

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I did this to my carbs and it made a huge difference. It will overflow quite a bit more but it doesn't hurt anything. Pay attention to everything Freez has to say, he knows what he is talking about. I am president of the Freez fan club.
 

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Discussion Starter #15
:)) Thanks for the complement protraxrptr17. I am glad people find this useful.
 

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So when the clear tube is put to the side of the carb, how does it look at the bottom, slack wise? I can't tell if there is a bit of a loop at the bottom.
 

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Discussion Starter #17
The slack or the length of the tube does not matter. The longer it is, the more fuel you will waist, but it will not effect the measurement of the float level. You only need to worry about not bending and pinching the tube closed. The tube should be able to connect to the bottom of the carb and make a smooth bend and stick out and inch or so above the split in the carbs.

I personally use a tube in length just over 1 ft.
 

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okay, if I use a foot long tube I see there is a bit of slack in the tube at the bottom. Won't it effect the 3mm measurement if the loop at the bottom hangs lower down? This is where I get confused.
 

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Discussion Starter #19
No the length or slack have no effect on the 3mm. Sounds strange but it’s true. Gravity and air pressure is constant no matter how long the tube is.

You can even try the following. Measure the 3mm with the least amount of slack. Then give it the most slack and you will notice the fuel will level itself inside the tube and return to the 3mm mark. Always keep the fuel supply open when you do this.
 

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After much searching and reading about the clear tube method :wtf: I now understand. Thank you so much for taking the time to explain this for all of us, makes perfect sense now. :lmao: :tup:
 
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