How To Properly Clean a Carburetor on a Motorcycle or ATV

How To Properly Clean a Carburetor on a Motorcycle or ATV

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
Thanks for watching!

About the Author: Michael Flood


  1. This is a great video, I wasn't confident stripping this carb down at all, but after watching this I stripped, cleaned and reassembled in a couple of hours. Thanks Guys 🙂

  2. Hi rocky mountain!! grat vids!! Con you see me video? I don't know whats appens with my bike, I tested everything and doesn't works fine :S
    wr 250 – 2004 No funciona bien

  3. Hey RM! i have a problem with my Kawasaki kx250F and the problem is the bike is backfireing like in this video (not my vid)  me and my dad has been adjusting the valves 4 times and changing piston and rings every time as the compression is al gone after just 2-4 hour of riding on the track. the 5th time we submitted the bike to a workshop and it did the same thing again after a few hours of riding… what can it be? why is it backfireing? why are the piston rings burned down after just 2-4 h on the track? may it be the carb jetting? or may it be valves in some strange way? or may it be the ignition? only thing i know is that the bike has been working corectly for the first 2 years of my own and that i have paid 1000$ for that "reparation" on that workshop and have been buying piston, rings, gaskets and shims for 620$ every time we adjusted the valves by our own. 

    Im from sweden so i dont have the best writing skills in english ^^

  4. Thanks for the video.
    How can i remove the plastic air vent hose joint that looks like a T ,just beside the hot star knob?

  5. Hello and thank you for your in-depth video. I have a Suzuki Vinson 500 and it had Sat without being started for about 2 years. I wanted to get it running again so I bought a carb rebuild kit, tore the carb off and apart and cleaned it, as well as replaced all the jets, springs, and gasket and then reinstalled it. I then replaced the air filter, spark plug, and oil/oil filter. New battery as well. After doing all this, I then completely drained the old fuel and replaced it with 93 oct. When I try to start it now, it'll start but will only continue to run as long as the choke is on. No matter how long I warm it up for, as soon as I try to slowly turn the choke off, it'll stall. It will do the same if I even just touch the throttle as well.
    I'm not extremely well versed in engine repair and this is actually my first carb clean/rebuild, so I'm assuming I did something wrong when I reassembled the carb. Can you please give me any ideas as to what I can do to maybe adjust something in or on the carb to fix the issue please?
    Thanks for your time.

  6. How do you safely remove the throttle shaft screw for a second cleaning after it has been secured with medium thread locker? 

  7. Hello, Iv just received a second hand 39mm FCR to go on a honda air cooled FMX650 lump (same as an xr650), It looks identical to this one. Iis from an 05 bike, looks in good condition but definitely been apart due to the rounded off screws on the bowl. If you don't mind I have a couple of questions…

    Firstly I have already ordered an upgrade an upgrade accelerator pump spring, is it a good idea to fit it? The one in it does look 'tired' to me. And is there any other internal parts worth changing out at the same time

    Second, I am looking on ebay at an adjustable leak jet but wondered what it does and if it is something worth fitting while rebuilding the bike, if it counts for anything I'm fitting a 10.5:1 piston, forged conrod, stage1 cam and Kibblewhite complete rebuild kit.

    Thirdly, and lastly, I am documenting the build as the Ugly Duckling Project and as such want to film the carb rebuild. I was going to use your video as a guide in the background, would you mind me doing this? I will give FULL credit as to what I am following and referring to while performing carb surgery lol

    Off topic, would you believe that the carb fitted directly onto the Honda intake rubber!! I mean the thing is of a Kwak, not only is it the perfect ID/OD but the locator tap that stops it spinning even fits directly into the notches on the rubber… I could not believe it =D…. As far as air intake goes it will be directly attached to a 150mm mushroom so won't be starved of air, which is a potential issues from what I gather if usng factory air boxes.

    Anyway, if your reading this thank you for taking the time and if you can answer the questions I would be over the moon.

    All the best

  8. I've been having a problem with my 250 Raptor for a few years now.  When it's in N or if I have the clutch in & I give it gas it's fine.  When I put it in gear & start to take off, it slowly boggs out.  I had a friend of mine who owned an ATV shop fix it & it happened again when he brought it back to me & I test drove it.  He took it back, "fixed" it again & it was fine for a few rides.  It happened so much that I just stopped riding it all together.  Can you please tell me what could possibly causing this to happen?  He said it was bad gas but it runs fine in N & when I have the clutch in.  I need to drain the gas & clean the carb sometime soon but I know that's not the issue.  I'd apprecaite any suggestions.  Thanks!

  9. This is literally the best how to I swear. Ive never had time to do the carb myself ive always had someone else doing it , but this time my wallet was empty so what the hell why not right? Followed every step in the video nd long behold the accelerator diaphragm was corroded bad I mean BAD!! Also my main nd starting jets most definitely need to be replaced. Leaving rusty liquid nd rust dust all over the place. Thank God I found out before anything else happened! Thanks much appreciated. ——Andrew

  10. Please Can anyone tell me why when I crank my fourwheeler all it does is rev very loud as if it were on full throttle and the exhaust gets flaming red from being hot

  11. Do you guys ever measure the float height, also whats a good indicator that the float is not set correctly. Thanks for the great videos.

  12. hey, I'm wondering if this will finally start my ATV because I've changed the spark plug, ignition coil, starter solenoid relay, magneto starter coil, and battery but nothing and when I turn on the gas switch gas won't leak even after 30 min. do o have to clean or buy a new carb….Help!!!

  13. I have a 2008 KTM 250 XCF, the bike only runs when the choke is fully open, as soon as I turn the choke off the bike dies, even after letting the bike warm up for a few minutes. I am thinking that maybe one of the jets is plugged up. Do you think that cleaning the carburetor thoroughly will help the bike run with no choke. It has a brand new K&N air Filter so I know that's not the issue. Any help would be appreciated

  14. @5:04 I tried praying carburetor cleaner down the fuel line and it does not squirt out the accelerator/throttle nozzle. How can I trouble shoot a possible clog?

  15. Hey Team, Thank you for making this video. I had issues with my Bike Carburetor.
    This Video gave me a good understanding about how to go ahead and clean the Carb, The Jets were blocked, once i fixed this my bike staring issue is fixed. 🙂

    how do i get in touch with you over Email ? just in case i've any queries,

  16. I need to replace the top and bottom gasket on my carb. Do I need to use sealant on them or just put the gaskets in dry?

  17. really wish you would have told me to count the ammount of turns on the air fuel screw befor hand.. I have no idea how to set that

  18. sorry iam brazilian and dont understand what you talk at 10:57… the white plastic spacer? what is the correct name, u can write here? thanks!

  19. can anyone help got an 06 yz250f. first of all bike takes forever to start. bike is backfiring and hang idling. wont idle unless idle screw is adjusted pretty high. cleaned and replaced the jets. any other suggestions?

  20. ugh a friend guided me with pulling my carbs for a clean , didn't finish disassembling it by the time he left. so for a solid week they've been off and he told me to study the shit out of manual, but reassembling it intimidating for me as a newbie.

    anyway you guys used carb cleaner in this video right? cant that damage the o rings? my friend emphasized to not apply carb cleaner to the o rings but my dad recommended I dont take them off. you didn't take them off. what gives

  21. Could tell me the number of turns of the fuel(pilot) screw,i install aJD Jetting Jet Kit and i do a airbox mod, and my
    crf250x used to turn on the first without problems, now discharge the
    battery and does not start, I have to kick 3 minutes to work, what can i do?

  22. Hi, i have a very annoying problem with my honda cr85. if anyone can help me figure this problem out, it would be greatly:

    My bike has too much smoke coming out from the muffler. WAY too much, It has a hanging idle when i rev it up while its idling. (also while riding). i changed the spark plug to see if it would fix the problem but nothing. i adjusted the air screw to factory specs which is 2 turns out but it didnt make a difference. i even turned the airscrew out more than 3 turns and i didnt notice a difference. then i turned the air screw in till it seated lightly and didnt notice a difference. ironically, the bike didnt stall either time when the screw was too far out or too far in. i thought initially that this problem occured from using fuel from last year but it doesnt seem to be the case. it started happening when i was trail riding. i was going pretty slow so it mustve done something. then there was alot of smoke, and the bike stalled. i started it back up and rode home. i even replaced the spark plug but the problem is still there. i took the carb apart and took all the jets apart and used some carb cleaner. they were clean anyway. i also did notice when tipping the bike over slightly, fuel would leak from the carb. i diagnosed that problem as being a stuck floar bowl and fixed it. please please help me out with whats going on.

  23. Do any carb rebuild kits include the Accelerator Pump and Air-cut diaphrams ? mine look like the ones in the video…destroyed from carb cleaner..
    Do I have to buy OEM ones separately?

  24. That was a Great how to video!! I like how you explained where each of the circuits, bolts, and holes are located on the carburetor while your were spraying it down. It was really helpful when you would state what tools you were using when disconnecting pieces!! Have a Great day man

  25. I didn't remove the throttle shaft screw before rotationg the control arm and now the whole arm is stuck and i can't push it back down, How do you fix this?

  26. awesome video. ordered a rebuild kit from you and used this video to assist. Thanks for putting these how to videos together.

  27. This was the best video ever. I've never taken anything on my bike off and repaired it. I actually got the carburetor off, cleaned it, and made the correct adjustments by following manual. My bike was bogging down while going full throttle. Now I can full throttle and keep going. Thanks for this video I would've never attempted due to not knowing what I was doing.

  28. please, could you tell me if the all piece (its seems like a little car) on the 5:33min is assembled with a plate? I pulled it out and it was separated

  29. If you fuel has been left in an FCR carburetor for a season the mid body of the carb. must be removed and plan on replacing the mid body flange gasket. I can't tell you how many modern 4 strokes carbs (KEIHIN FCR specifically) are not delivering fuel properly because the mid body gasket and o-rings are in poor condition.

    In addition to spray carb. cleaner in the slow circuit ports without mid body removal and proper cleaning just makes it worse. RM-ATV, this video is slightly irresponsible in not explaining that or at the very least requiring the entire unit and all parts to be washed clean of carburetor cleaner.

  30. Ran into a little problem when I put the slide valve plate back in with a new o ring it has play back and forth so when I give it gas I can hear it chatter. What am I doing wrong?

  31. Thanks for the help. This worked great for my first time. I'm leaking gas, so i have to try again, but i wouldn't have been able to do anything if it wasn't for you! Thanks again!

  32. Thanks for this great video 👌👌 , I follow step by step your instructions for my outlaw 525s and everything was so easy. Thanks again, you saved me at least $300 , that's how much they charge me for a full service like this at the shop. 🤝🤝🤝🤝🤝. By the way I thought you did only powder coating but I see you are a complete MacGyver .Lol. ☝️☝️☝️

Leave a Reply

Your email address will not be published. Required fields are marked *