CV Carburetor Cleaning HelpBefore you get started, you'll need a few phillips and flat head screwdrivers and a can of carburetor cleaner at a minimum. A lot of screws in these small carburetors are delicate/poorly made. Choose screwdrivers that fit well into each fastener. Sometimes inserting a phillips head screwdriver into the screw and then giving it a couple of taps with a small rubber mallet can help. I'm talking about somewhat gentle taps though, not trying to hammer or beat the screwdriver in. If a screw starts to strip, you may opt to leave it alone if it's in an area that is not as essential to clean in your situation or you could try to remove it with small vise grips and then replace it with a good screw. Be very cautious along the way so you don't mess up the carburetor or any of it's parts.
This article goes a little beyond the most basic carburetor cleaning, but still does not remove every single component. If you want the most basic cleaning you would focus on making sure the bowl is clean, the pilot jet, the main jet, cleaning all passages in the carburetor's body, and inspecting the diaphragm and slide. If you have a specific issue, be sure to address the parts of the carburetor that may be directly related. For example, if your accelerator pump is not functioning don't skip over it while cleaning.
If you're totally uncomfortable with the idea of cleaning the carburetor, some choose to replace it since many can be found for Roughly $30 or sometimes less. Be aware that sometimes replacing the carb will result in tuning issues. Sometimes the new carburetor uses a different main jet or pilot jet and won't function properly. Most commonly the main jet is the problem. In this case you may need to swap the jet(s) from the old carburetor (clean them first) into the new carburetor or go through a bit of a tuning process.
Wear gloves and eye protection while working with carburetor cleaner or other chemicals.
You'll need to begin by removing the carburetor from the scooter. This video shows carburetor removal. It will also be of use if you have a factory sealed carburetor.
If you didn't drain the fuel from the carburetor prior to or during removal drain it now. You should see a screw on the very bottom of the carburetor's float bowl with a barb beside it. Loosen the screw and fuel should drain from the barb. Sometimes there will be a hose attached and a small assembly with a drain screw in it at the end. In that case, loosening the screw in the end should drain the carburetor, then you can remove the hose from the fitting on the bowl and set the assembly aside.
Remove the 2 screws holding the top of the carburetor on. Keep a little bit of pressure on the cap as you remove it slowly because there is a spring under it.
Remove the spring and then carefully remove the slide and diaphragm assembly.
Remove the needle and the components that hold it in the slide/throttle valve. There's usually a plastic piece, the needle and a clip attached, and you may have an o-ring below the needle clip.
Inspect the diaphragm for cracks or other damage and replace necessary. Anything that causes a leak would change how the carburetor functions. Clean the assembly with carburetor cleaner.
Make sure the clip on the needle is secure and that the needle is not bent. If the needle is bent, replace it. Clean it with carb cleaner.
Set the parts that you just removed aside in a small group. Keeping parts grouped together as you move to different bits of the carburetor will make reassembly easier. Clean any parts that you have not already cleaned.
Remove the plastic cap covering the automatic enricher/bystarter by carefully pulling it straight up.
Remove the 2 screws holding the metal piece that secures the enricher into the carburetor body and clean the metal parts off.
Pull the enricher out of the carburetor and clean the needle and barrel with carburetor cleaner. Wipe off the outside and plastic ares with a cleaner/degreaser as well.
Set the enricher related parts aside in their own small group.
Remove the clip and the downward facing hose from the vent port on the side of the carburetor. The hose should be replaced it it is cracked or damaged. Wipe it clean and be sure that it's clear inside, not clogged.
Now switch your attention to the float bowl. Remove the screws attaching the bowl and separate it from the carburetor body.
Carefully remove the gasket from the bowl. Wipe it off, inspect it for damage, and set it aside.
Unscrew the accelerator pump jet and remove it. Be careful because there is a small spring and ball under it.
Turn the bowl over and let the ball and spring fall out, being sure not to lose them.
Clean each with carburetor cleaner and then set aside. Be sure the jet is free of obstructions. When cleaning jets you can spray through them with carburetor cleaner and/or compressed air.
Set those parts aside, grouped with your float bowl gasket.
Now look at the bottom of the float bowl again. Remove the screws securing the accelerator pump cover, keeping pressure on it because there is a spring below it that you don't want to loose. Remove the cover, spring, and diaphragm. Many carbs will also have a rubber boot above the pump that slides off. Inspect the diaphragm for cracks or tears and clean the parts with carburetor cleaner and set aside.
Remove the o-ring gently, inspect it, wipe it off, and place it with the rest of your float bowl and accelerator pump parts.
Unscrew and remove the float bowl drain screw. Clean it with carb cleaner and put it with the rest of your float bowl parts.
The float bowl should now be bare. Clean it with carburetor cleaner, being sure to spray through any holes and passages. Use compressed air as well to spray through passages. If you have a lot of buildup or grime you may need to scrub the bowl with a toothbrush. You can also fill it with cleaner and allow it to soak to make cleaning it easier. Once clean, set the bowl aside.
Now we can start focusing on the carburetor's body.
Remove the main jet by unscrewing it.
Clean it with carburetor cleaner. Spray through it with carb cleaner and compressed air if you have it.
Hold the main jet up and look through it to verify that it's completely clear before setting it aside. Jets may be soaked in carburetor cleaner for stubborn clogs and/or use the bristles from a toothbrush or plastic cleaning brush to clean it. Be extremely cautious not to damage or enlarge the orifice with any method of cleaning or it will alter how the jet functions.
Unscrew and remove the atomizer. Mine required a 7mm socket or wrench.
Clean the atomizer with carb cleaner and compressed air. Look through it's central bore and verify that it's clear.
Check the holes in it's sides as well to be sure they're clear.
Remove the pilot jet. Sometimes called the idle or low speed jet.
Just as with the other jets, clean the pilot jet with carburetor cleaner and compressed air. Check all openings. In the pics below you can see a pilot jet that was clogged, and then the open jet after cleaning. I used a plastic bristled brush to help break the obstruction loose. You can cut off a single bristle from a thin/fine wire brush or one strand of something like a speaker wire and use it, but again be very careful not to scratch, enlarge, or otherwise damage the jet. Soaking the jet in carburetor cleaner may also help to remove whatever is clogging it.
Next we can move on to the float and related components.
Before anything is tampered with, have a look at the float height. Sit the carburetor upside down, so the float is facing up and the top of the body is on a flat surface. Standard float height usually allows the float to sit parallel with the top of the carburetor, or I suppose you could say perpendicular to the body of the carb. It's easiest to see this if you look at the seams on the float.
In most cases that float setting works well. If you have previously set the float to any other level for tuning purposes, record the old float height by measuring from the carburetor body to the float seam in an easily identifiable location and making a note of it. Float height should not change during the average cleaning job, but it's better to check and be prepared just in case.
Remove the screw that keeps the float pin in place.
Lift the float assembly straight up out of the carburetor body, being careful not to lose anything. Here you see the float needle still hanging from the float. It may stay in the carb. That's fine. Remove it as well if so.
Slide the float pin out and clean it with carburetor cleaner.
Separate the float needle from the float if you haven't already.
Clean the float needle with carburetor cleaner. Usually the float needle has a coated tip. If the coating has worn off it will need to be replaced.
Clean the float with carburetor cleaner being careful not to bend the tab where the float needle once hung. Inspect the float for damage or cracking. The float needs to be sealed to work so if you find any cracks forming or fluid in the float it should be replaced.
The float parts should be set aside in their own group.
Now the underside of the carb is mostly stripped. There is still more that could be removed here, but it's not usually necessary.
Locate the idle mixture screw on the side of the carburetor. Turn the screw in until it gently stops, counting the amount of turns. Make a note of the amount of turns needed to get the screw seated. This will allow you to reset it to the same position later. Now unscrew it and remove it. There should be a spring behind it, so be careful not to lose it. Some carbs may also have an o-ring and/or washers behind the screw.
Remove the spring and anything else behind the screw, being sure to note the order in which they came out. Clean the parts and set them aside into their own small group.
Now switch your attention to the opposite side of the carburetor. Remove the two screws which secure the throttle bracket and accelerator pump trigger and remove the bracket assembly.
Clean the bracket and check that the lever which activates the accelerator pump moves freely.
Now you can access the air cutoff valve. Remove the two screws in the cap covering the air cutoff valve. Keep pressure applied as you remove the screws because there is a spring under it.
Remove the cap, spring, and diaphragm. Take note of how the diaphragm was installed. Clean each part and inspect the diaphragm for holes or cracks.
Remove the o-ring that was under the air cutoff valve cap. Wipe it off and inspect it for damage.
Now you should have a collection of parts in small groups plus the large carburetor body and float bowl.
Hopefully you've been cleaning the parts along the way, but you still need to clean the body of the carb. Spray it with carburetor cleaner and take the dirt and grime off of the outside. That's not the most important part though. Now you need to use carburetor cleaner in every nook and cranny and passage in the carburetor's body. Use the straw on the carb cleaner can and spray through every opening you can find. Be careful because carb cleaner may shoot out of a different opening at you. Go easy at first, till you see where it comes out. Once you're confident that you've given attention to every area, use compressed air to blow out each hole and passageway.
If you have access to one, an ultrasonic cleaner is very nice for cleaning carburetors. I have had luck cleaning carbs that I otherwise was unable to save using an ultrasonic cleaner because it can clean areas that I cannot reach. It can even break up gunk and deposits in jets so you can avoid poking or prodding at them in most cases. I got this one for roughly $60 at Harbor Freight and use it regularly for parts cleaning. I use a solution of degreaser, such as Simple Green, and water for most tasks and let it work for at minimum 15 minutes. Usually longer. If using an ultrasonic cleaner, I still clean all areas with carb cleaner and compressed air, but it do it after using the ultrasonic cleaner.
Now you should have a bunch of clean parts waiting for re-assembly.
I'll begin re-assembly by getting the float bowl and attached accelerator pump parts back together.
Insert the ball, then spring, then accelerator pump jet into the opening shown and screw the jet in. It needs to be tight, but not a lot of torque is required with these small brass and aluminum parts.
Looking at the very bottom of the carb, reinstall the o-ring into the opening as shown.
Slide the diaphragm through the hole in the center of the accelerator pump housing so the stem faces what would be the top of the carburetor.
Sit the spring in the center of the diaphragm and line the cap up so the spring seats in it. Apply a little pressure while you install and tighten the two screws that secure the accelerator pump cover.
Make sure the pump moves easily and returns. If you have a rubber boot for the accelerator pump, install it now.
Reinstall the float bowl drain screw and tighten it. If your carburetor used a remote drain or hose it may be easier to save that for later attachment.
Install the float bowl gasket into it's receiver groove. They can be difficult to seat. If the gasket seems too large to fit it may be due to swelling from contact with chemicals. In that case, you may find chilling the gasket so it shrinks slightly comes in handy. Once the gasket is installed, the float bowl should be ready go so set it aside for later.
Install the idle mixture screw, spring, and any other hardware such as o-rings or washers into the appropriate opening in the side of the carburetor in the opposite order as they were removed.
Screw the mixture screw in until it stops. Don't force it as if you're tightening a bolt or screw. Then back it out the number of turns that you should have noted when it was removed. It may require additional adjustment once installed on the engine.
Move to the air cutoff valve. Install the o-ring as shown.
Insert the diaphragm into the carb, being sure to note the orientation. One side should have a nub that seats in the carb and the other has a seat to accept a spring.
Place the spring in the seat of the diaphragm. Then line the spring up with the air cutoff assembly's cap. Hold some pressure on the cap while you install and tighten the screws to fasten it to the carb body.
Now the throttle bracket can be installed.
Line the bracket up so that the holes align with the threaded holes in the carburetor's body. Make sure the accelerator pump lever sits on the roller on the throttle. Install the two screws. You should see that there is a long screw and a short screw. The long one usually goes through the lower hole that passes through the accelerator pump setup.
Verify that the throttle stop lines up with the throttle and that the accelerator pump assembly is actuated if you open the throttle before moving on.
Push the automatic enricher/bystarter into the carb body.
Slide the retaining plate into the groove on the enricher.
Install the 2 screws to secure the retaining plate.
Slide the enricher over on, being careful with the enricher wires.
Slide the vent hose onto the carburetor and install the clip.
Flip the carb upside down and install the pilot jet. Like other jets, it needs to be tight enough that it's secure but not extremely tight.
Screw the atomizer into the carburetor body and tighten it.
Install the main jet into the atomizer.
Now we can start installing the float and related parts. Slide the float pin through the float.
Hang the float needle on the tab on the float as shown.
Carefully lower the float into the carburetor so that the float needle lines up with it's seat in the carburetor and so that the pin aligns with the groove in the carburetor. Then install the screw that keeps the float pin in place.
Make sure the float moves freely and doesn't hang up. Check the float height to be sure it's the same as it was when you disassembled it. If the float height has changed you may need to bend the metal tab on the float to change the height.
The underside of the carburetor should be completed now and ready for the float bowl to be reinstalled.
Make sure the gasket in the float bowl is still seated all the way around. Put the float bowl on the carburetor and secure it with the float bowl screws. If your carb had a hose on the drain or a remote drain, this would be a good time to reinstall it.
We're almost done. Now it's time to reinstall the needle, slide, diaphragm and the rest of the parts into the top of the carb.
Double check that the clip is secure on the needle. If your carb included an o-ring under the needle clip, slide it onto the needle. Put the needle through the hole in the center of the slide/throttle valve.
Place the plastic retainer on top of the needle and clip.
Drop the diaphragm/slide/needle assembly into the carburetor. The needle will need to slide into the hole at the bottom. use care installing it so you don't bend the needle.
There is a nub on the diaphragm that needs to be aligned with a groove in the carburetor so it will properly seat.
Insert the spring into the slide so it sits over and around the plastic retainer above the needle.
Align the spring under the cap into it's seat or onto the post, depending what your cap is like. Hold pressure on the cap and install the screws.
Now the carburetor should be totally assembled and ready to go back on. If you have any "spare parts" leftover, identify what it is and where it came from and go back and correct the issue.
You can find carburetor installation help in the video at the beginning of this post. Watch for leaks once the carburetor's bowl is full and when the engine is first running. If you use a vacuum petcock or fuel pump, remember that it may take a little cranking or priming for the bowl to fill with fuel so the scooter can start.
Hey Brent,I was reading your carb cleaning tech article,maybe I missed it,but I didnt see mention of the choke/enricher jet/orifice inspection and cleaning..Thats a problem area for gunked up carbs..The enricher has a tube that runs into a separate chamber in the float bowl,it feeds thru a tiny brass or just a drilled hole within the bowl(.021" or so for a 50cc 2T).Most of the later model carbs have a very lean (read EPA std.)start jet,I like to open up the lean ones .002" bigger than supplied..Dont try this at home kids!! 
