# 2-cycle carburetors - to remove/replace or rebuild?



## dudtalk (Jul 18, 2013)

My garage is quickly filling up with an assortment of 2 cycle lawn tools ... some are mine while others were purchased by my son and "stored" at my place. When time allows I attempt to repair these machines ... and have been fairly successful. The problem that gives me the most headaches is fuel issues related to problems with the carburetor. I currently have two Echo machines that exhibit fuel starvation issues. Each has good compression and have spark ... but the lack of fuel to the carb prohibits them from running. I have gone as far as pouring a small amount of gas into each carb and testing them ... they start right up and then die when the fuel runs out. 

The one issue that confuses me is that when I attempt to prime the carbs I get nothing but air. The fuel lines are fine ... but no gas. 

Every project should have a budget. Either a machine is worth saving or not. In the case of a carb we are talking anywhere from a carb rebuild to a complete replacement:

- A carb replacement can run from as low as $20 to as much as $80 or more. The units that I have issues with run in the high $20s to high $30s.

- A carb rebuild kit can run as little as 1/3rd to 1/4 the cost of a new carb.


My questions to the forum are:

1) Why, when everything else seems fine would fuel NOT flow into the carb when the primer bulb is depressed?

2) At what point do you rebuild vice replace a carb? I have taken each of these carbs apart and rebuilding them would not be difficult. My concern lies in the chance that rebuilding will not fix the fuel issues. I have researched and found that many carbs have internal check valves that are not serviceable. If they are the problem then the only alternative is carb replacement.


I would appreciate any advise from the group. Thanks ...


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## Don L (Jul 14, 2012)

If the carb hi and low mixture screws are'nt adjustable I do'nt attempt a rebuild.If I see signs of water damage or build up of deposits I do'nt attempt a rebuild.
If the metering diaphragm is hardened up and I do'nt see any other poblems I try a kit.
The "Z"brand carbs seem to me to be the worst.
I have taken carbs back apart to salvage the kit just to try it in another carb of the same model.It's hard to break the habit of trying to salvage carbs.


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## 30yearTech (Sep 14, 2006)

Pretty much agree with Don on this one. 

Carburetors with the high & low carburetor adjustments are generally found on older pre C.A.R.B. units and you can enjoy a successful rebuild on these. 

Newer ones were meant to be replaced rather then rebuilt, so unless the problem lies with a plugged filter screen, stiff diaphragm or bad / sticking inlet needle, then your chances of having success with a rebuild are small.

Failure to draw fuel through the carburetor with the primer bulb is a good indication of a check valve issue in the carburetor.


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## dudtalk (Jul 18, 2013)

30yearTech said:


> Pretty much agree with Don on this one.
> 
> Carburetors with the high & low carburetor adjustments are generally found on older pre C.A.R.B. units and you can enjoy a successful rebuild on these.
> 
> ...




Thanks for the info. Is the check valve you are referring to the valve underneath the primer or one of the valves built into the carb that is not serviceable?


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## Don L (Jul 14, 2012)

The only time I have ever seen one of these check valves was when I had to go to a Stihl silver level training class and they had a carb that was machined in half to show the check valve in the body of the carb.There is no way to get to it without destroying the carb.
They said not to use carb cleaner on these as it would swell the rubber check valve closed.I suspect this is what happens with ethanol.


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## 30yearTech (Sep 14, 2006)

dudtalk said:


> Thanks for the info. Is the check valve you are referring to the valve underneath the primer or one of the valves built into the carb that is not serviceable?


The valve under the primer bulb is serviceable, but usually the ones in the carburetor are the ones causing this issue. They are not sealing so the primer bulb draws in air instead of creating a suction that draws the fuel into the carburetor. This can also be the cause of the run issue.


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## Rentahusband (Aug 25, 2008)

So basically if these carbs do not have mixture screws, do not bother with a kit? Generally if a new carb is only $10-$15 more than the kit, I will suggest to the owner that a new carb would be a more cost effective repair.


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## 30yearTech (Sep 14, 2006)

Rentahusband said:


> So basically if these carbs do not have mixture screws, do not bother with a kit? Generally if a new carb is only $10-$15 more than the kit, I will suggest to the owner that a new carb would be a more cost effective repair.


Many carburetors cost considerably more then a kit, so they may be worth taking a look at to see if it's something like a stiff diaphragm, plugged filter screen etc, if nothing stands out, replacement is usually the best option. I replace a lot of carburetor on commercial weed trimmers, as a rebuild is a time consuming venture, that rarely pays off.


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## Don L (Jul 14, 2012)

30yearTech said:


> Many carburetors cost considerably more then a kit, so they may be worth taking a look at to see if it's something like a stiff diaphragm, plugged filter screen etc, if nothing stands out, replacement is usually the best option. I replace a lot of carburetor on commercial weed trimmers, as a rebuild is a time consuming venture, that rarely pays off.


The frustration factor should be considered too,when you try to save the customer money on a repair and it do'sent work no one is happy.


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## Rentahusband (Aug 25, 2008)

Don L said:


> The frustration factor should be considered too,when you try to save the customer money on a repair and it do'sent work no one is happy.


So true!!! Saving the customer money is sometimes not worth the frustration!!


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