In this video we’ll show you how to properly clean a carburetor on your motorcycle or ATV. Note this process will vary from each carburetor, so always refer to your service manual for proper procedures and specifications. You’re going to want plenty of rags and some carb cleaner along with your service manual and a few standard tools. You’ll notice we’ve already gotten the carburetor removed from this bike. If you need assistance with this, refer to your service manual. First, we’re going to want to clean the outside of the carb really well. If there’s dirt on the outside we want to get it off now before we begin opening the carb up. Once we’ve got the outside really clean just start at the top. Remove the valve lever housing cover by removing the two Allen head bolts holding it on. As you can see, ours is really dirty. We’re going to go ahead and clean this off
right now just using a little carb cleaner and a rag. Next, we’ll remove that throttle shaft screw. When the screw has been removed we can rotate the control arm and raise the slide up and remove it from the carburetor. Watch the front slide plate, because sometimes it will stay down in the carburetor. There are a couple of different places you do not want to clean with carb cleaner, and this O-ring is one of them. The carb cleaner will make the O-ring swell and deform and will most times ruin the O-ring. The other two places you don’t want to get carb cleaner is the diaphragm in the accelerator pump assembly, and then this carburetor happens to have an air cut valve. Not all carburetors will have this valve, but it also has a small diaphragm that will get ruined if sprayed with carb cleaner. The best way to avoid this is removing these components before spraying any cleaner inside the carburetor. At the bottom of the carburetor you’ll find a fuel screw and then your float bowl plug, and you’ll also see an accelerator pump cover. Keep in mind this carb is off an ’07 WR250F. Your carb could look a little different, especially if it’s a two stroke carb. Now we’re just going to back that fuel screw out. If your screw is stock you will need a flat blade screwdriver to remove it. After that, remove the three screws that are holding the accelerator pump cover on. When those are out we can pull the pump cover off and out of the way. Under that you’ll find a spring and your diaphragm. Go ahead and remove the spring and then gently pull the diaphragm out noting its direction so it can be reinstalled correctly. The next step is to loosen and remove the float bowl plug. Doing that will give you access to both the pilot jet and the main jet. Next, we’re going to work on removing our float bowl. There are four little screws that hold this on, so go ahead and remove those. A lot of times these will be Phillips head screws which are easily stripped out, so make sure you’re using the appropriate screwdriver for the job. Go ahead and pull that float bowl off. Set that down on the table. Next, we’re going to push the float pin out. With that out of the way we can pull the float assembly out of the carb. Set that down on one of your clean rags. Next, remove the float needle from the float. Now is a great time to inspect it for wear. Now, we’re going to pull the main jet out of the carburetor. Do this using a 6 millimeter socket. Sometimes it’ll come out with the needle jet. We’ll separate these later. Now we can pull the plastic spacer out and then remove the pilot jet and the starter jet using a flat blade screwdriver. The next part that needs to be removed is the air cut valve. As I mentioned before, not all carbs will have this. There are two screws that hold the valve cover on. When those are out pull the cover and that will reveal the spring and the diaphragm. Go ahead and set all those parts down on the clean rag. Now that we’ve got everything out of the carburetor that could potentially be damaged by carb cleaner, we can begin cleaning the body of the carburetor. When you’re spraying out the carburetor it’s best to use the supplied hose with the carb cleaner. You want to spray it into every little nook and cranny to make sure you get all the dirt and sand out. It’s important to make sure every hole and passage is clear of everything. When spraying into a hole or opening, make sure the cleaner comes out somewhere else. If it doesn’t it could mean that something is blocking that circuit. I’ve cleaned the air cut valve circuit. Now we’re cleaning both the air jets on the back of the carb. Next, we’ll clean the fuel inlet, make sure there’s nothing in there. Then, clean all three holes where your starter jet, main jet, and pilot jet sit. After those are clear, clean out the fuel line coming from the accelerator pump. You can see that that squirt through just fine. We’re just going to spray cleaner through every hole making sure everything is clear and clean. Now we’ll move to the top of the carb. Spray out the slide and the hot start circuit. When those are clean we’re going to remove the choke plunger assembly with the wrench. When that’s out just clean the plunger off and spray the circuit out making sure everything is clean. When it is, go ahead and reinstall the choke assembly. Next, we’ll move to the slide assembly. On this slide valve there are four little wheels that we’ll remove to clean. Keep in mind yours may be a little different. When the wheels are off spray the slide off really good, and then we’ll clean each of the wheels as well. Once those are clean, reassemble the slide, making sure all the parts make it back to their original location. The next part we’re going to clean is the float bowl. Spray it out with some carb cleaner and make sure it’s wiped out really well. After that we can remove the leak jet from the bowl. This requires a small screwdriver, but be careful not to strip it out. When that’s removed we need to make sure all the channels that run to and from the accelerator pump are clear and free of any dirt or sand. After that, spray off both the air cutoff valve and accelerator pump covers. Wipe each cover off removing any dirt or dust. Now we’re going to spray out all the parts we’ve got sitting on the rags with compressed air. This will just reassure us that nothing is blocking any of the ports or channels in each piece. After we get both covers blown out, carefully take each jet in hand and blow air through it to make sure it’s clear. At this point we can separate the needle jet and main jet using an 8 millimeter wrench and 6 millimeter socket. Go ahead and blow both those out as well. Then, after we’ve cleaned each part and blown everything out, we can start putting the carburetor back together. Reinstall the leak jet, and then we can reinstall the starter jet. Once that’s tightened down, next is the pilot jet. Go ahead and drop that into place. Tighten it down. After that we can install the plastic spacer and then the needle jet. With all these jets we’re just tightening them down as far as they can go. There’s no setting for how many turns you need to go, so keep that in mind. Then after the needle jet comes the main
jet. It just threads into the end of the needle jet, so just tighten that down using a 6 millimeter socket. Be careful not to over tighten this because we don’t want to break it off. The next step is to reinstall the float needle. Once you’ve got it into place sit the float down into the carb making sure the needle is sitting down in the supply hole. After that, just slip the float pin into place. Now that the float’s in place we can attach the float bowl back onto the carb. Make sure everything lines up and goes together smoothly. Reinstall each of the four float bowl screws and then tighten them down. Again, you want to be careful when tightening each of these. You don’t need to crank on them because you’ll either strip them out now or strip them out when you try to take them off again. We’re just going to snug them down. Next, reinstall the accelerator pump diaphragm. Make sure the little metal button is facing up or out. Then, hold the spring in place while you set the cover down into place. Install all three screws and tighten each of them down. Again, you don’t need to crank on these, just snug them down. Next, install the float bowl plug and tighten that down. Then, we’re going to move onto the air cut valve. Make sure we got the small O-ring in place, and then position the small diaphragm into place. Next comes the spring and then the cover. On this carburetor there’s a little bracket that screws on with this cover that holds the valve cover breather hose in place. Go ahead and snug both of these screws down. The next part to install is the slide valve. Make sure you’ve got the O-ring on your slide valve plate and install that with the rest of the valve into the slide of the carburetor. You’ll need to make sure the valve level rollers slide into the slits on the slide valve as you slide it down into the carburetor. We’re going to apply a little medium strength thread locker to the threads of the throttle shaft screw before installing it into the throttle shaft assembly. Go ahead and tighten that screw down, and then we can install the valve lever housing cover. Make sure the cover O-ring is in place, and then reinstall both Allen head bolts and tighten them down. The last part we need to install is our fuel screw. We’re running one of the Tusk adjustable fuel mixture screws that allows us to adjust the air fuel mixture ratio on the fly. Simply slide it up into the carb and carefully thread it in. Once you lightly seat it, thread it back out to your original setting by counting the number of turns. Once that’s in place we’re done with the carb cleaning. Go ahead and reinstall the carburetor back onto the machine and go ride. If you have any questions, refer to your service manual or call in. Rocky Mountain ATV/MC carries all the parts and tools you need to thoroughly clean and completely rebuild your carburetor. Check us out online at www.rockymountainatvmc.com.
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