A carburetor has a significant role in the motorcycle fuel system. It consists of many parts and can seem like something complicated if you get in touch with it for the first time. We are going to explain to you in detail and as simple as possible all the things that you should know about motorcycle carburetors, including the one that we find the most important, and that is how to repair a motorcycle carburetor.
So how to repair a motorcycle carburetor? Remove and disassemble the carburetor. Take off the float chamber and the floats. Detach the jets and air or fuel adjusting bolt. Once you have removed all the parts, clean them and replace the damaged ones. Use WD-40 to spray the pieces, put the carburetor back together, and adjust it.
If you want to learn more about a carburetor, continue reading as we will also mention signs that will warn you that there is something wrong with the carburetor as the how to fix these problems.
Table of Contents
How to Fix a Motorcycle Carburetor?
Before you start dealing with the problem and fixing it, you need to get the appropriate tools to perform the job. As I said before, if this is the first time you get in touch with a motorcycle carburetor, it could look a bit frightening, but don’t worry, it is not as complicated once you get started.
Make sure to follow our step-by-step guides, as we will cover the most important tips and tricks you need to know during the process.
Here is a great article about How Does a Motorcycle Carburetor Work, so click on this link if you want to learn more.
Step 1: Preparation
The first thing you need to do before starting any work on the carburetor is to protect yourself. What I mean by that is to get yourself safety gloves and glasses since you will work and be in touch with chemicals and gasoline that can damage your skin and cause some kind of irritation that will stop you from repairing ( and you haven’t even started yet).
Clean the space where you will perform the repair since you don’t want to cause even more damage on the carburetor with some dirt.
Tip: Working in a clean area gives you more awareness of where your tools and parts are, so you will get the job done much faster than if your working space is in a mess.
Step 2: Remove the Carburetor
A circular clamp or two screws hold the carburetor on the inlet manifold. Turn off the main fuel supply and empty the float chamber ( the chamber base of some carburetors has a small bolt along with a hose- look at the picture “A”); on the other hand, on the majority of carburetors, the control cable and slide (B) can be easier to remove after you detach the carburetor from the engine.
Step 3: Disassemble the Carburetor
The first thing you need to do is remove the float chamber (if you have already removed the slide). There are usually four bolts holding the float chamber, and you should see them if you rotate the carburetor upside-down.
Note: Three bolts or a wire clip can be found on some units.
After removing the bolts, you will need to perform a sharp tap using a plastic handle of a screwdriver, and the reason for doing that is loosening it out of the gasket.
Step 4: Remove the Floats
Once you have removed the float chamber, you will see:
- primary jet ( also called the pilot jet)
- the main jet
- overflow pipe
- floats
Remove the floats first because they are delicate. Brass or plastic material is used for making the floats. Some types of floats are prone to leaking, and you should check them as soon as you remove them to see that there is no gasoline in them.
The floats should have a free range of motion on a compressed pin.
You need to remove this pin carefully because the aluminum stand which holds it can break easily.
Tip: hold one side while you extract the pin out.
Step 5: Remove and Clean the Jets
A two jet system is integrated into most of the classic motorcycle carburetors. The primary jet (A) is in control of fuel flow out of idle to one-third throttle openings, while the main jet (B) controls the other two-thirds. Since the primary jet is small, it can get restricted or blocked, and this will lead to poor running conditions during the early time of throttle opening.
You need to clean the jet or replace it in order to fix this problem.
Note: This problem can be solved using a motorcycle choke. If you wish to learn more about a motorcycle choke and how to fix it, click on this link.
Step 6: Remove the Air or Fuel Adjusting Bolt
The air or fuel adjusting bolt is one more thing that needs to be removed from the carburetor body. Look at the bolt’s relative location on the slide to determine which type is placed on a specific carburetor.
If the bolt is placed on the engine side of the slide, its purpose is to adjust the fuel (fuel adjusting bolt), while if the bolt is placed on the air filter side of the slide, then its purpose is to adjust air ( air adjusting bolt).
Note: Notice the Bolt Position.
A tapered screw has an effect on the strength of the mixture, which can be lean or rich. It works along with the primary jet throughout the first third of the throttle opening. Check the position of the bolt before removing it. There are a number of turns set from fully closing the bolt, which need to be made during reassembly.
Step 7: Clean and Visually Inspect the Parts
Once you have removed all the parts from the carburetor, you need to clean and visually inspect all of them to determine if there is something wrong with them. Use carburetor cleaner to clean every spot on the carburetor body and blow it out with compressed air.
CAUTION: Wear eye protection glasses as you clean the carburetor because dirt and liquid will come out and can get in your eyes and irritate you.
Step 8: Reassemble the Carburetor
Reassembling the carburetor is the opposite process to disassembling. Examine the flat heights before reattaching the float chamber. The mixture and the engine’s condition will be affected by the float height. You can adjust the height, and to do so, you need to bend the small metal tang lightly. This metal tang puts pressure on the needle valve.
The fuel delivery into the chamber will be cut off if you bend the tang to the valve, decreasing the fuel height. The requested height calculated from the gasket face all to the top of the floats with the help of a ruler is detailed in a workshop manual.
Step 9: Protect the Parts
Use WD-40 (or something similar) to spray all the parts before putting everything together. If you don’t plan to reinstall the carburetor back to the motorcycle for a longer period (in the case of the renovation as an example), you should put it in a plastic bag that will protect it from external conditions.
Step 10: Fine-Tuning
Fine-tuning the air adjusting bolt is sometimes required when you complete overhauling the carburetor. Before you start to make any adjustment, you need to allow the engine to get warmed to its working temperature once you return the carburetor. You should be careful while adjusting. If the engine accelerates during adjusting, it means that the adjustment was right on point. If the engine decelerates, on the other hand, it means that you should reverse the adjustment.
What to Replace When Rebuilding a Motorcycle Carburetor:
A few parts need to be replaced during the motorcycle carburetor rebuilding process.
- the needle valves
- the float
- ventils or jets (if they are too messy to clean)
- every gasket that you previously took off
Here is a great article about How Does Motorcycle Ignition System Work, so click on this link if you want to learn more.
How to Recognize Carburetor Problems?
There are three main problems regarding the carburetor:
- an incorrect adjustment
- a mixture too lean
- a mixture too rich
The good news is that there are signs that will help you recognize what kind of issue you are having problems with.
The carburetor is a very simple motorcycle part. Its primary purpose is to deliver the exact air-fuel mixture once the rider uses a throttle. As with all the other mechanical devices, the carburetor also needs to be serviced and tuned. It is inevitable that your carburetor will wear out over time, but you can extend its lifetime with proper maintenance.
Note: You need to run the proper diagnostics to repair your carburetor.
1. An Incorrect Adjustment
An incorrect adjustment means that the balance between two or more carburetors and the air-fuel bolt is disturbed, leading to previously mentioned symptoms. Multicylinder machines have these signs appointing to incorrect adjustment:
- inconsistent acceleration
- weak fuel economy
- backfiring
- misfiring
- stalling engine
- jingling sounds coming from the clutch
- weak overall performance
2. A Mixture too Lean
The fuel-air ratio is off when the carburetor runs lean, and the reason for that is too much air being delivered by the carburetor.
These are the most obvious signs of a lean mixture:
- sudden acceleration
- light gray or even white spark plugs
- light gray or white muffler end pipes
- backfiring ( when closing the throttle)
- The exhaust header pipes are getting blue ( on chrome installations)
3. A Mixture too Rich
The fuel-air ratio is off when the carburetor runs rich, and the reason for that is too much gasoline being delivered by the carburetor.
These are the most obvious signs of a rich mixture:
- slow acceleration
- no need for the choke from cold starts
- black muffler end pipes
- black spark plugs
- bad fuel economy
- intense gasoline smell while the motorcycle is in the neutral position
Here is a great article about What Is Better, Motorcycle Carburetor or Fuel Injection, so click on this link if you want to learn more.
1. How to Fix Incorrect Adjustments?
Poor maintenance leads to this state most of the time. The engine creates vibrations that can rotate the bolts responsible for the right mixture. You need to check multicylinder balancing bolts and correct them if this is the case.
2. How to Fix Lean Mixture?
This state is mainly caused by inappropriate fitting like exhaust systems, replacement carburetors, or air filters. If the fuel level in the float chamber is not enough and is placed too low, not enough amount of fuel will be sent through the main jet.
A slow-speed fuel adjusting bolt can be found on some carburetors. This bolt controls the fuel-air mixture when the rpm is in the lower range. Other carburetors have an air adjusting bolt. When you rotate this bolt clockwise, it will decrease the quantity of air that enters the carburetor, and because of that, the mixture will get enriched.
Note: use a shop manual to see the proper settings.
3. How to Fix Rich Mixture?
This state is mainly caused by messy air filters, although it can also be caused if there are inappropriate fitting like exhaust systems, replacement carburetors, or air filters. If the fuel level in the float chamber is placed too high, a rich mixture will be created. You need to clean the air filter to fix this problem.
Here is a video for you to watch How to Clean a Carburetor in a few steps:
Conclusion
This article was written for everyone who has troubles and finds it hard to fix the carburetor. Don’t neglect the carburetor and its maintenance because it could lead to other fuel system problems.
We hope that this article was helpful and you have found all the information you looked for.