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Discussion Starter · #1 ·
Hello,
I've been looking at used weed eaters/wackers in my neck of the woods and have found many low priced ones that need carburetor work/cleaning.
I am quite familiar with 4 stroke carburetors because I have rebuilt/cleaned more than a few for different motorcycles and a few snowblowers.
However, I'm looking at a dark hole when faced with a 2 stroke carb.
Would the cleaning procedure be similar to a 4 stroke one?
I'm very tempted to pull the trigger on one of these 2 stroke weed eaters but am not sure what I'd be getting into LOL!
Any insight would be very appreciated!
TIA :)
 

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Better off buying a new carb that won't have issues. They are Cheap enough, usually under 20 shipped.
 

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My experience has been that they are very similar. I have a toro 3650 2 cycle snowblower and rebuilt the carb several years ago same basic parts as my 4 cycle Ariens. Others may disagree but it is just my opinion.
 

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Let's talk older carbs, the newer OHV carbs are more complicated.

4 cycle lawnmower carbs are simple.

4 cycle snowblower carbs are the same but larger, however they have more holes in the throat and a replaceable Welch plug.

Both are gravity fuel fed.

2 cycle snowblower and lawnmower carbs are simple, very simple. Some 2 cycle snowblower carbs are tricky to remove the 2 bolts.

However, 2 cycle blower, chainsaw, and weed wacker carbs are more difficult. The holes are smaller, there is no float, the needle valve has a spring. They have a built in fuel pump called a diaphragm. This always needs to be replaced as it gets older, it gets hard and no longer is flexible to pump the fuel. To order carb parts, you need the carburetor number off the carb. The 2 major manufacturers are Zumi and Walbro. If there is no carb number, do not buy it.
 

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i would agree that most of the time it is almost cheaper to buy a kit with a new carb with fuel lines and everything. you can usually get them for about $20. small engines use a carb that is not too bad to work on but in most cases generally require a carb kit and fuel lines.
 

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The most recent two-stroke I worked on had the same carb as a four-stroke. Course that is not true of many others I have worked on.
Especially of the ones mentioned above. (Weed, blower, saws.)
Can you do it. Definitely. And many people here have.
 

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Discussion Starter · #7 ·
To order carb parts, you need the carburetor number off the carb. The 2 major manufacturers are Zumi and Walbro. If there is no carb number, do not buy it.
Your insight has prevented me from purchasing a few that I was interested in. Their carburetors and parts are obsolete! Thank you! (y)
 

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Discussion Starter · #9 ·
Thanks everyone for your insight. It has been an eye opener. I don't know much ... but it is a more than when I posted my question.
I will continue searching and most probably come back with more questions. :cool:
 

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Gotta' agree with the "get a new cheap carb" folks.

Did it for my recently acquired (free) Toro 2-cycle single stage and as well for 4-cycle lawn mower.
 
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The small two stroke engines use "cube" carbs and have no float bowls. Big difference between them when cleaning or repairing.
 
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Weed whacker carbs are simikar yet quite different than a 4c carb like on a snowblower, since the 'whacker does not really have a defined "up" orientation. Thus, they are not gravity fed, but rather have a small diaphragm fuel pump driven by crankcase pressure on one side, and a metering diagphragm on the other, that basically provides tne same function as a float. A lot of folks miss the pump diaphragm and valves, since they just look like parts of the gasket on that side . . . but if if that piece gets stiff, things don't work well. On most 2c carbs of this style, replacing both the seal/pump side as well as the metering diaphragm will take care of pretty much most problems . . . they are about the only parts that degrade. Considering the expense of most of the Zama or Walbro type carbs, myself, replacement would only be a last resort - theh really are that easy to work on.
 

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Discussion Starter · #14 ·
Weed whacker carbs are simikar yet quite different than a 4c carb like on a snowblower, since the 'whacker does not really have a defined "up" orientation. Thus, they are not gravity fed, but rather have a small diaphragm fuel pump driven by crankcase pressure on one side, and a metering diagphragm on the other, that basically provides tne same function as a float. A lot of folks miss the pump diaphragm and valves, since they just look like parts of the gasket on that side . . . but if if that piece gets stiff, things don't work well. On most 2c carbs of this style, replacing both the seal/pump side as well as the metering diaphragm will take care of pretty much most problems . . . they are about the only parts that degrade. Considering the expense of most of the Zama or Walbro type carbs, myself, replacement would only be a last resort - theh really are that easy to work on.
Great information for a newbie to 2 stroke carbs. Thank you! (y)
 
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Nane brand carb manufacturers have carb numbers, no name manufacturers have none.

The biggest problem getting the carb number, many times is hidden behind something, sometimes the air filter cover, housing. If you do not see the number, that does not mean it will not have one. If it's a name brand, Stihl, Redmax, Echo, ..... it will have a number. However, sometimes the kit becomes obsolete.
 
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Nane brand carb manufacturers have carb numbers, no name manufacturers have none.

The biggest problem getting the carb number, many times is hidden behind something, sometimes the air filter cover, housing. If you do not see the number, that does not mean it will not have one. If it's a name brand, Stihl, Redmax, Echo, ..... it will have a number. However, sometimes the kit becomes obsolete.
Echo seems pretty good with thier use of Zama carbs . . . one of my recent rebuilds was my 20 year old-ish hedge trimmer, and absolutely everything was widely available. Granted, that only applies to Echo/Zama, but it does tend to indicate that Zama overall has decent part support, since the Echo carbs are stock Zama - nothing odd . . .

The other source of part information can be the mfg. of the unit itself, even if the carb is unmarked.
 

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A string trimmer or chainsaw can't use a float bowl carburetor because the machine must sometimes operate upside down. Float bowl carburetors won't function when inverted.

The small cube-shaped impulse/diaphragm carburetors deliver fuel regardless of their orientation. The vacuum created inside the crankcase volume acts upon and flexes the diaphragm which functions as a positive displacement pump.
 

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A string trimmer or chainsaw can't use a float bowl carburetor because the machine must sometimes operate upside down.
Honda took this concept to the 4-Stroke Engine with the Handheld GX series, AKA 360-degree-inclinable mini four-stroke technology. Here's a cool cutaway animation of how it works:
 
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