Picture of How to Clean a 2 Cycle Engine Carburetor
Read this article for professional carburetor cleaning steps and advice. Learn why you may want to clean your tool's carburetor with or without a rebuild kit.

Cleaning a small engine carburetor usually gets done as part of a carburetor rebuild, but there are a number of reasons why cleaning a carburetor without rebuilding it is also a good idea for tool owners. 

Organize Parts into Rows During Procedure

Properly cleaning a 2-cycle engine carburetor means completely disassembling and reassembling the unit.

We explain the steps to disassemble and reassemble an example 2-cycle engine carburetor below, and we also explain the correct way to clean a carburetor while it's still disassembled.

Carburetor Disassembly Steps

This carburetor disassembly, cleaning, and rebuild demonstration is performed on a carburetor from a Ryobi 2-cycle grass trimmer. Steps for other carburetor cleanings will be similar to these.

Tip! Carburetors have many small parts. Keep carburetor parts organized in the order that they are removed (like in rows) to make reassembly fast and accurate.

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Step 1: Remove the Bottom Plate

Picture of Remove the Bottom Plate
On The Bottom Side of the Carburetor,

Unscrew the two screws that affix the lower cover plate to the carburetor body.The bottom plate is held on by four screws for some carburetor models.

Step 2: Remove the Diaphragm and Diaphragm Gasket--Separate Them if Needed.

Picture of Remove the Diaphragm and Diaphragm Gasket--Separate Them if Needed.
The carburetor diaphragm will come off easily after the bottom plate is removed.

The diaphragm gasket will often stick to the diaphragm when removing it from the carburetor body. If the diaphragm and diaphragm gasket are stuck together, they must be carefully separated from one another to be cleaned later.

Step 3: Remove the Needle Valve Mechanism

Picture of Remove the Needle Valve Mechanism
The needle valve mechanism consists of three parts: a needle, a lever, and a spring.

It will be visible in the body of the carburetor after the diaphragm is removed.

Unscrew Jet Valve Retaining Screw

The needle valve mechanism is held into place by a retaining screw.

Unscrew the needle valve retaining screw to release the mechanism from the body of the carburetor.

Make sure to hold the spring-loaded mechanism in place as you remove the screw. This will stop the valve parts from flying across the workbench.

Gkempf11 months ago

I have a craftsmano weed eater with out a primer bulb,carburetor been off the the unite for a while,I've replaced the carb,but now I don't remminber how the fuel li

oakback4 years ago
I recently did this for a Stihl trimmer, which has a Walbro carb (though it looks just like the one in this instructable). I bought a parts kit from a location dealership and did pretty much everything explained here, except replaced old parts with new.

For me, the hard part is tuning the thing afterward. I still haven't been able to get it to run right and idle right (I can get it to do one or the other), even after finding the factory tuning specs online and following that.
H454 oakback3 years ago
There Is one screw for idle(I) and one for everything from idle and hirer(H). Set the idle first than the high, after its warmed up. If you Messed up it totally, turn all in (to the right) than back about 1 - 1.5 turns. Then go from there (plus) or (-).  Somtimes there is three screws - Idle(I), LOW (L)-first half of RPM range, and High (H)-upper half RPM range. Tune in order of lowest RPM to Highest.

Also check your air filter, gas line, and important and often missed - the fuel tank breather tube (I have a Stihl chain saw that always has problems with breather tube).A bad breather tube creates a vacuum lock, their by stopping fuel flow.

Check the spark for a bright blue consistent spark.

Also Try fine tuning oil/gas ratios -That can have have a Very noticeable effect on tuning and performance( especially in smaller engines)- more oil tends to run a little richer.
RCline4 years ago
It's not a good idea to soak down rubber gaskets/diaphragms with carb cleaner. It will weaken them and sometimes destroy them. Carb cleaner is nasty stuff. I had to learn the hard way.
toolrepair (author)  RCline4 years ago
The intended purpose of the article is to demonstrate how to clean a carburetor when a rebuild kit is unavailable. In this situation the risk of any damage while cleaning the carburetor is greatly outweighed by the high cost of a replacement carburetor. As far as carburetor cleaner potentially causing damage to the rubber components in the carburetor, that is true and a real risk. In my experience I have found some carb cleaners to be much more prone to causing this damage than others. It seems that the higher quality carb cleaners greatly reduce the risk of this type of damage.

Tool Repair Guru
I Work at a small engine repair shop and we work with Ryobi equipment fairly often and we are able to get rebuild kits for the carburetors. Most small engines use ether Walbro or Zama carburetors. From my experience the most common reason for a dysfunctional carburetor is the filter screen in the carb body getting clogged or the lever that opens the needle is bent too much in the wrong direction letting too much or not enough fuel in to the carb. I might have missed it but I did not see anything on resetting the hight of this lever. Depending on the type of carburetor this hight can very but in most Zama carbs the lever is flush with the top of the carb body. On a Walbro it is recessed a little bit below the top. Each company has its own metering gage for its carburetors.     
toolrepair (author) 4 years ago
We also made an instructable of Mark with showing you how to properly do this in a video! Hope it helps, I know some of us don't like to read as much as watch :)

Click Here for the Video
jptrsn4 years ago
Really good: clear instructions, and good photos. I'll likely give this a try on my trimmer once the grass stops growing!

I second the vote for a 4-cycle tutorial for the mower that goes with the trimmer!
Great Job. A lot of people are afraid to tear into a carb. This enplanes it very well.... 4 cycle next?
toolrepair (author)  biker_trash_13404 years ago
Thanks for the support @biker_trash_1340 -> Hopefully we can find the time to get a 4 cycle guide up here :)

Tool Guru