Updated: Sep 23, 2019
It happens to all of us, we go on a week long trip and come back only to find our 2 stroke steed no longer starts or just plain won't idle! What could it be?! It's the carb.... There is a TL;DR at the bottom if diving into a carb really is not for you. Cleaning a Bing carb is one of the simplest carbs to clean, and is a wonderful carb to cut your teeth on. Worse that could happen is you lose a jet or *gasp* get gas on your hands. So lets dive in! This tutorial is not your average step by step tutorial. It's based upon a diagram of majority of the parts in a carb. This method both explains their importance of these parts and best way to clean them. Look for bold writing for key cleaning points. Below is Bing carb wonderfully out of focus and done up in paint by my 5 year old nephew, but it gets the point across!
Intake: Delivers the atomized gas and air to the engine. Be aware that some air leaks may form where the intake connects with the carb itself. To minimize leaks be sure to press the carb on with one hand and then tighten the screw with the other hand. Choke: Choke is on when down and off when up. With this particular model of carb, when you give the moped full throttle it will shut the choke off, just something to be aware of when having difficulty starting your bike. To simply describe the choke this lever moves a "door" that closes off the entrance of the carb, thus enriching the mixture by allowing more gas and less air. Primer: This is a spring loaded pin the goes into the float bowl and presses directly on the "float" (we'll get into that later) thus raising the level of gas in the bowl. I primarily use the primer to verify that the carb bowl is actually getting gas. Once full, gas will leak out around the primer pin, verifying that yes your carb is getting fuel. Idle screw: This screw controls rpms (revolutions per minute) that your bike will run at when you are not applying throttle. Turning the screw in (to the right) the bike will idle at a higher rpm, turning to the left will make the bike idle at a lower rpm. Float bowl: The "bowl" houses the jet/s, float, and float valve. and screws on as it is threaded inside on the bottom. *Attention!* Some times the float bowl will leak for no apparent reason, be sure to check the gasket (seal) between the float bowl and carb body. The very old ones are made of cork and sometimes break into little bits making the carb non functional because of gas and air leaks. Also, do not over tighten the carb bowl if it won't stop leaking. Next we'll get into the most daunting part that keeps majority of people from cleaning their carb! The interior of the float bowl!
I have cropped out majority of the parts that do not pertain to the "daunting" float bowl interior. As you can see there are six parts....that's right SIX not including the float bowl. You can do this! 19 - This is the float bowl, sometimes there will be sediment,dirt and other non so fun treasures in here. Be sure to clean the bowl thoroughly prior to reassembly with carb cleaner and a small wire brush or tooth brush. 18 - This is the float bowl gasket. This is often made out of cork or old rubber and may be cracked or deteriorating. Don't try to bandage up broken or cracked gaskets it all just ends in frustration. This is my choice for new float bowl gaskets. 17 - This is the actual float. Very old floats are made of cork or foam. Sometimes these floats can become "waterlogged" or in this case "gas logged" if this is the case your carburetor will leak everywhere no matter how much you have scoured the inside. The easiest is just purchasing a new carb float from here. 16 - Is a float pin, in bing carbs it just pushes in and out from the side and can easily fall (or may need pliers for removal), so either way take care not to lose said pin. Now comes the VERY important pieces. 15- Is the pin for the float valve. This valve with the help of the float regulates the amount of gas that is in the float bowl. As the motor burns gas the float will lower allowing gas to enter the bowl, as the bowl fills up the float will rise closing the valve to prohibit the flow of gas. Sometimes this pin can become lodged up inside the carb body, use extreme care when removing it as to not damage it. As you can see in the photo below the pin has a rubber tip. Sometimes this rubber tip becomes hard and does not seal properly, letting gas flood the float bowl. Once removed , I would take either compressed air or carb cleaner and be sure that it can freely flow through the hole in the carb body.
14 - This is called the Main jet. Majority of the time, this is your issue. This provides majority of the fuel for the engine. If this becomes plugged in any way it will keep your engine from starting or running properly. The jet its self is easy to remove with a flat head screwdriver and firm pressure to keep from stripping the head of the jet. If your carb is relatively clean but your bike runs like dog poo, I would go straight to this item. I find that one tine from a wire brush or a old guitar string works well for cleaning these. You want to be able to see light through the center of it, if you can't see light and a perfect round hole, keep cleaning! (compressed air works very well here) 13 - This is called an atomizer. Gas passed up through this and is broken down into separate atoms for more efficient combustion in the engine. Majority of the time in a bing carb this will not be removed as only the jet comes out. If the atomizer comes out be sure it too is clean. It will have tiny holes on the side of it that some times get gunked up. THAT'S IT! Sure there are more parts on the top portion of the carb but in my experience I have found that these items are very rarely the problem. If the atomizer stays in, it is literally 5 pieces to keep track of and clean. Most of the mopeds that I purchase or come in for repair are simply a carb clean away from being a running bike. Quick easy way to turn a $200 moped into a $600 moped. Here is a entire rebuild kit, if you just want to replace everything and make it right. If we didn't cover all of your questions check out our Forum often times our shop staff spends some spare time here and can help you trouble shoot. If not one of out community members will surely give you a hand! TL;DR : Remove carb.Take the float bowl off clean it. Remove and clean the interior of main jet (flat head screw in the middle). Reassemble. If diving into a carburetor is not your cup of tea... I recommend this super easy replacement carburetor. Just be sure to run the stock air box. Or just contact us on our home page and set up a time to come in! Thanks for reading! Stay tuned for our next tutorial ! - Steen