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It’s my 1st post, so I hope you guys find this useful. I have spent years messing about with the carbs on the 660 raptors, and I picked up a few tricks in the process. The basics on how to set up the carbs have been posted, so I am not going to explain more on that. What I will tell you is how to set up the stock carbs to release some hidden HP, and make that rappy go like it has never gone before.

This post is a modified version of my post on another forum, so some of you might have seen this before.

So, let's get started.

You need to remove the front plastics, and the fuel tank. This should be a 10 minute job, and a great explanation can be found in the stick section of this forum.

Before you start you need to decide if you are going to run with the airbox lid on, or off. The carb settings are different for both options.

If you are going to run with the stock air cleaner or an air cleaner without the billet adaptor, you need to run with the lid on. It keeps the air cleaner in place.

Now if you are wondering what the best setup is for running with the airbox lid on, here is what you need to do. Remove that stupid rubber snorkel, and throw it away. No matter how you modify it, it drops power output, so just get rid of it. I have proven this on like 50 raptors, using my own dyno, so just take my word for it. Next, remove the lid and you will find there is two “tubes” underneath. Cut all the plastic “tubes” open, so you end up with no tunes at all.

If you are worried about water or mud getting into the airbox stop here.

If not, and you need the lid to hold the stock air cleaner in place, you can cut about 3 to 4, 2 “ holes into the lid to get air in there. Try and space the holes evenly to create even airflow around the air cleaner.

Then, if you want to do this correctly, get yourself a jet kit. I prefer the Dynojet kits and I have proven it on my dyno that the Dynojet needles work best with the no airbox lid setup. The GYT-R and stock needle either supply too much or too little fuel.

Again, have a look at the carb sticky to see how to install the jet kit.

Now, this is something you can try and experiment with, but my dyno seems to indicate the following works well. If you run with the lid on, use the Dynojet slider springs, but if you run without the lid, use the stock slide springs.

Install the Dynojet needles as per the kit instructions. You might want to experiment with the clip positions, Maybe 1 clip higher or lower is better, but the instructions are generally quite close.

Next, drain the fuel from the carbs and remove them. I did not take the throttle cable out. It is possible to work with the cables attached. 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 fuel level at a later stage. You need to move the clear tube from the one to the other carb to check both float/fuel 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. A good tip is to support the carbs, insert the screw driver, and with a hammer, give the screw driver 2 to 3 nice firm taps. This usually helps the screws to loosen up, before you start removing them. Another good tip is to get new steel screws if you can, and throw those damn stock screws away. 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 times. (I used the Dynojet stage 2 kit settings. It might be different for other jets)

For a modified lid, get yourself size 25 pilot jets, and run them around 3 turns out. If you run without the lid, I found that the 27.5 pilot jets are required, also using 3. to 3.5 turns out.

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 air or pilot jets.



Install the main jet as per the Dynojet instructions. Again, look at the carb sticky to see how this is done.

Now to check the float levels. THIS IS THE KEY TO RELEASING THE FULL POTENSIAL OF THE RAPTOR POWER.

To give you a base point you can use the method the Yamaha manual recommends. With the carbs hanging at 90 degrees with the openings that connects to the motor facing down. Move the carbs between the 90 degree position and upright and look at what the floats are doing. When the carbs are the right way up, the floats are hanging fully opened. When you start turning the carbs to face 90 degrees down, you will notice the floats move and suddenly pause. It will pause for a little while, but if you keep turning it to make the openings face down to the ground, they will move again. You need to find where they pause, and keep it there. This position is where the floats touch the needle valve pin, but not compress the needle valve spring. Measure between the split (place where the float bowl and carb comes together) and the of the float shoulder. It should measure around 14 to 16 mm. The image is showing you how to hold the carb in the right position. It shows 13mm, in the picture, so try make them slightly larger.



The floats on ALL stock raptors are out, and needs to be adjusted. It is set to low at the factory. 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 it down towards the bottom of the float will lift the float level. Bending it towards the top of the floats will lower the float level. Generally you can bend it lower, then put it back in the carb, check if it is measure14 to 16mm. If not start the process again, till you get it more or less correct. Do small amounts of bending at a time. The tang is very sensitive.

Once you are done, you might run into a small problem. The floats might not open fully, and you might find that the motor sucks the carbs dry. With the float bowls on, turn the carbs upright, and hold them in the normal mounting position. Now blow into the pipe that connects to the fuel tank. You should be able to blow air easily through the fuel pipe. If you turn the carbs back to the 90 degree angle, it should stop flowing air. Also try holding one float closed at a time and do the same process, making sure both carbs flow air when you blow on the fuel hose. Don’t press to hard, or you might have to readjust that levels again. If it does not flow air, or it is hard to blow thru the fuel pipe, 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. If you are not sure how well it should flow, take one float off, and remove the needle valve. Now close the remaining float by turning the carb upside down and blow on the fuel pipe. It should now flow air easy and you can get a feeling for how it flows.


The below picture shows the float level mod. Take a small little file or sharp knife and file/cut down the little plastic stopper at the back of the float. DON’T shorten it, just take a 45 degree angle off it. Take little chunks of at a time. 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 air thru the fuel intake pipe when the carbs are the right way up.

Try not to cut them too far, so that the floats lie on the bottom of the float bowl. Remember do this very carefully, and little bits at a time.

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 struggling to go back in, make sure the clamp screws are loose all the way. Then dip your finger in same fuel and rub it inside the intake, See below. With the fuel still wet, the carbs will slide in real easy.


Now to check the float with the carbs in place. 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 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 screw on the bottom. Point the clear tube up and above the section where the carb and float bowl joins. Open it up 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 EXACTLY 3mm between the carb and the float bowl. Check both carbs. You will have to move the clear tube and go to both side of the bike to check the two carbs. Don't try checking it from the same side. See picture. PS. my finger is not pointing at the fuel level, it is only holding the pipe in place. The RED arrow is the place you need to use to check the float level against.



If it is not exactly at 3mm, close the fuel supply, drain the carbs and start again. I cannot stress enough how important it is to get it exactly at 3mm. 4 or 2mm is not going to cut it. Keep adjusting the float tang, till you get this right. Less than a 1mm adjustment is mostly what you need to get this right.

Then, if you like to go a step further, and release even more hidden horsepower. Remove the carbs, and feel inside those rubber intakes. You will feel that they are not matched to the intake ports. Get a Dremel tool, with a 80 grid sanding drum, and open those rubber boots up, so that they match the intake ports perfectly. Do this in stages, and with caution, and take your time, I you mess this up you will need new intake boots. Once done, clean them very well with fuel, and install them back where they came from, followed by the carbs.

Now 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.

One last thing. You will gain about 10% more power with this mod, and about 15 to 20% more if you remove the lid in the process, and run a high flow air cleaner. Throttle response will be much better, and you will feel the extra power. It also helps the bike to hold its power peak further into the RPM range, and you can stay in a gear longer, before having to select the next one.

I have done this to about 50 different 660’s, and they all show good power gains. A stock raptor picks up 2 to 3 HP from the float level mod and intake boot matching alone. It works even better when you add a better exhaust and air cleaner to complement this mod.

Try this, and you will not believe the difference it makes.

It will wake up that rappy of yours, and give it a whole new level of power.
 

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"Remove that stupid rubber snorkel," What are we talking about here esactly and location please im assumeing the little hose on carb with open end sticking streight up?. also i am trying to understand this part
"remove the lid and you will find there is two “tubes” underneath. Cut all the plastic “tubes” open, so you end up with no tunes at all." I understand the spelling misteak right "tubes" not "tunes" but i dont understand this part any pics to exsplaine? My wife has key to my lock which locks the seat down and it cant be removed so right now i cant take off the lid to look underneith for the momment. Can you help exsplane? Thanks for your valuble thread.
 

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I did these mods, and the difference in throttle response is amazing, instant rpm, and best of all its cheap. Freez has lots good Raptor info, dyno tested many combos and is a great resource to have.
 

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Welcome Freez, I've read a number of your posts on different forums, thanks for sharing this. Hope you stick around.

Looking from the side, the 3mm he refering to is from the seam between the carb bowl and the carb body. The carb bowl is the part you take off to get at the floats and jets. The fuel level will be 3mm above the split point.
 

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Thanks freez, glad you found your way over here. :thumbsup:

I've been posting up sixsixt's old text writeup of the clear tube method but it's great to have a more thorough post with pictures availible.

Edit: August 2013

Original pictures now offline, using this post to consolidate pictures until I get them all and figure out what order they go in Freez's original post.

Edit: March 2016

New forum software caps posts at 10k charachters so I can't modify the original post without losing part of it. Re-uploaded images here from OP's post.
 

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Discussion Starter #11
Thanks guys.

Ok, as they said, the rubber snorkel I refer to is the rubbery peace of tuber that fits onto the airbox lid. Remove it, it just drops power output. It has a single clamp, loosen it and pull it off. If you look inside the dynojet kit, they tell you to cut some restrictions out of it. Don't bother. Liek I said, just rip it off, and put it away.

Then the "tubes". I don;t knw what is the right word to descrive them, but remove the lid, and turn it upside down. Look at the way the air is comming into the lid. You will see there is two seperate passges or "tubes". Where they suck in clean air, they are wide, but the tube narrows towards the end where they lead into the airbox, assuming the lid is on. Those tubes restric airflow, so cut the tubes open. Meaning, take all the plastic inside the airbox lid out, so those tubes disapear. You will still end up with the two passges leading to the outside, of the lid, but don't mess with those.

I will try and get a puctire for you guys to see what the modified airbox lid looks like.

But, if you want the best power, the best is just to remove the whoel lid, and install a air cleaner wwith a billet adaptor. Thwen you don't need to bother with the lid.

I liek to install Outerwears airbox clovers on all the quads I modify. Thos eairbox cover will stop mud and water splaches from gettigng into the airbox. These things let air thru, but keep the other stuff out. I still advice peopel to be carefull aroudn water, but the cover works well.

Then, if your bike is already jetted, and you do the carb and intake mods, you most likely can go up a jet size on each carb.

Then, the 3mm.

Like they said, find the place where the carb and the float bowl comes together. Then with the carbs upright, or normal mounting position, measure 3mm up from the split.

A easy way to find 3mm, is to look at the carb. Find the split. Then if you look at it, and you move your eyes up a tad, you will see it has a shoulder, which goes over the float bowl and hold it it place. IF you go a tad futher up, you will see form the shoulder there is a 45 degree angle or support. Where that 45 degree angel stops, or joins up with flat body of the carb, that is 3mm. Mark where the shoulder and flat side meets, and you make sure the fuel level is level with that mark.

Hope that clears up a few things.

These mods have been tested over and over again. I personally have done around 50 raptors with these mods and the owners love it.

While you are working on the bike, make sure the valve gaps are checked and set correctly.

To put this into perspective. If you drag race over 300 ft, and struggled with a close competitor, these mods will give you 2 to 3 bike lengths over the other guy. You will feel the increase instantly, without even taking it to a dyno.
 

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Ok, i ve got another stupid question, :crazy:
i know understand the 3mm concept but, what is the correct way to push the clear pipe up against the carb? Ive found that this can be misleading dependend on how it gets pushed up against the carb.
Just as a point of interest: My floats was set at about 10mm.
 

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Discussion Starter #13
There is no special way or trick to hold the clear tube next to the carb. The only thing you need to worry about it that the fuel does not run out of the top of the tube. As long as the tip of the tube is higher than the fuel level, you’re fine. Then, move the tube close to where you can clearly see the 3mm line on the carb, and compare that to the fuel level inside the pipe.

Just remember to get rid of any air bubbles in the tube, before you measure the 3mm level. A couple of taps against the tube, will sort the bubbles out.
 

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few more valueble questons. The end of the clear tube is it suposed to be at? a certain level of the carb are above?

I now almost fully understand this method and will be doing it after next atv event dureing maintance like oil change clean the filter and I will also clean the carbs and check jetings and such.

So to go back stock i will need new air lid if i cut on it and also put back on the snorkle correct?
Will the fuel/air screw need to be mess with doing this mod?
And If i ride in heavy mud events should i keep snorkle on I thought of the prefilter for the k&n i got but still concern about mud /water geting into box. most trail and events are 98% dirt and mud free but some can get unexspectly muddy as crap cause they presoak the tracks for the 4x4 guys who like to tare it up. I sure aperciate Your reply back to my questions and thanks again for all the info pics and post.
 

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Discussion Starter #16
660RaptorR, yes QPR is my company.

Ok, last try to clear up the clear tube measurement. Get yourself a clear tube than fits the drain plug fitting on the float bowl. It does not have to be an exact length, but about 12" should be fine.

Attach the clear tube to the drain plug and bend the other end upwards. The open end should be higher that the mating surface of the carb and the float bowl. Any height is fine, so long as it is higher than the matting surface.

Just hold the clear tube high enough to prevent the fuel from overflowing out of the pipe.

The fuel level is not worried about how high you hold the open end. The fuel level will be consistent, no matter how high the open end is.

O, and don't close the fuel supply from the fuel tank, when you do these checks.

Look at the picture below, and try and figure the “path” of the clear tube. It is very visible, just keep in mind that the tubes passes behind the "fitting" that attaches the throttle cable to the carbs. You will see it comes out the top of the “triangular plate thing" and ends nearly at the top of the carb. I fit it like that, so that I don’t have to use my hands to hold it in place. You will get an idea of how I fit the clear tube. In the photo, the open end is nearly as high as the top of the carb. But again, like I said, a bit higher or lower than that is fine, it will not mess with the reading.

Try changing the height of the open end, and you will see the fuel level stay constant. That’s just how levels work.

Again guys, there is not specific high, just hold it high enough so that the fuel does not run out the open end. It’s that simple.

 

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thanks for info i tottaly get this method now and cant wait to try it out. on the other hand how about in muddy condition shuld the snorkle be left on?
 

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So what would flow more air: a lid that has been modified to the max (holes, baffles cut out), or an outerwears airbox cover (not the filter sock, the actual cover that replaces the lid)?
 
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