# Do I clean or replace FS45 trimmer carburetor



## G-Mann (Dec 29, 2007)

Have a Stihl FS45 weed trimmer that has a low idle and bogs down when hitting the throttle. Gas lines are good and so is the tank filter. Is it worth my time and effort to take apart and clean?

If you say just replace it, how about the cheap one's they sell on Amazon as replacements for $14.00-$20.00. Or should I buy the factory replacement?


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## geogrubb (Jul 28, 2006)

G-Mann said:


> Have a Stihl FS45 weed trimmer that has a low idle and bogs down when hitting the throttle. Gas lines are good and so is the tank filter. Is it worth my time and effort to take apart and clean?
> 
> If you say just replace it, how about the cheap one's they sell on Amazon as replacements for $14.00-$20.00. Or should I buy the factory replacement?


Have you tried opening the L circuit about 1/8-1/4 turn, go to the Zamacarb.com site, they have a lot of info on trouble shooting their carbs. And yes it is easier/cheaper to just buy a new carb than rebuilding the old one. Have a good one. Geo


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## G-Mann (Dec 29, 2007)

Well, I just replaced the carburetor with a new one. After calling the Stihl dealer and was told $27.99, less than $30.00 dollars out the door. If I had known this before I posted, I would have never posted to begin with.

Anyway, after taking it out of the box, I noticed that it did have threaded High & Low adjustments but, the limiter caps would not allow you to adjust at all! So I just took my soldering iron and melted them off.

After that, I mounted the carb with the factory adjustments still in place. I noticed it ran O.K. but had a slight delay when hitting the throttle. So I turned the Low speed adjustment out another 1/2 a turn and now runs better than ever!!

Two things I noticed with the new carb - the primer bulb filled with fuel 90% of its capacity compared to the old one. And 2 - it smokes a lot less at full throttle compared to the old one!


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## G-Mann (Dec 29, 2007)

Forgot to sat that the guy who sold me the carb told me to start using non ethanol fuel and to mix 2 ounces of Sea Foam per gallon of gas every time I buy it.


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## nbpt100 (Jun 1, 2015)

Non-ethanol fuel is a very good idea if you can find it. You typically have to get it at an airport or marina. Or buy the premix which can get expensive if you use you machine a lot.

Sea foam and similar additives are one of those things that every one has an opinion on. I tend to only use it if a machine is running rough. 

I always add Stabil to my gas cans prevent water condensation from wrecking havoc. Sea Foam does have stabilizing qualities as well as cleaning qualities but is more expensive than Stabil.
I would not worry about the primer bulb only filling up to 90% of its capacity. As long as it is running fine. I have seen that before on 2 cycle carbs.


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## Rentahusband (Aug 25, 2008)

I recently overhauled a carb on a Troybuilt trimmer which did not help. Bought an aftermarket carb for $20 and it ran perfect. If I can get a new carb for under $30, I will do that vs overhauling. I am lucky to have non-oxy fuel at the pump. Is about .60 higher but worth it.


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## finaprint (Jan 29, 2006)

I am one that has never used any fuel additive in anything (cars bikes, small engines) ever, and no issues at all with it. I DID sell seafoam and I DID give the spiel about how 'wonderful' it is but telling you guys, there' s no magic there. NONE. 

Run the carb dry at the end of every use and ethanol fuel then does nothing to the piece of equipment. Got 5 saws and trimmers and zero issues at all. I use nothing in them and the fuel gets stored for months at a time, it just has to be in fully sealed containers. Still using last years gas and running fine the ethanol here is mandated at 10% it often runs up to 20% real world though, the fuel sellers are crooks. 

It's an opinion only but it's been working for 40+ years. I loathe fuel additives, they only bleed your pocketbook.


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## 30yearTech (Sep 14, 2006)

It's great that some can use older ethanol laced fuel and not have problems. 

Here in Central Texas it causes issues. It is very aggressive on the rubber components and fuel lines in the fuel system. I see it on a regular basis. It can cause premature fuel line failure, stiff diaphragms, and check valve failure in carburetors. 

I have found (in a continuing 40 + years of experience) that seafoam is a good additive that helps keep fuel systems clean and reduces the amount of varnish or build up caused by old fuel. Ethanol shield is another product that is also proving to be good at reducing the effects of ethanol on fuel system components. 

Another good option is the pre-mix ethanol free canned fuel, it's stabilized and good for at least 2 years and has no ethanol.

I also recommend running units dry for storage, but this does not insure trouble free starts down the road.


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## PhillT (Sep 16, 2015)

I am green with envy. $30 for a brand new carby???
Un-believable!! I have been quoted over $100 for on for my line trimmer her in Australia.
Hopefully I can get some good advice here, once I get enough post up to be able to link to the video of the issue.


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## PhillT (Sep 16, 2015)

Forgot to mention, the issue I am having is bogging down under throttle, but pulsing also.


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## nbpt100 (Jun 1, 2015)

PhilT, if making some slight adjustments to your low mixture and perhaps the high mixture screw does not help then you may need to rebuild it. Carb kits in the US are generally $10 plus or minus. I hope they dont screw you on those too in Australia.

Also make sure you have a clean or relatively new fuel filter.

You could try some Sea Foam or similar first...... but it may be just better to rebuild it.


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## PhillT (Sep 16, 2015)

nbpt100 said:


> PhilT, if making some slight adjustments to your low mixture and perhaps the high mixture screw does not help then you may need to rebuild it. Carb kits in the US are generally $10 plus or minus. I hope they dont screw you on those too in Australia.
> 
> Also make sure you have a clean or relatively new fuel filter.
> 
> You could try some Sea Foam or similar first...... but it may be just better to rebuild it.


The rebuild might be the go.
This is what it is doing:-
https://www.youtube.com/watch?v=YGu5u1dWPAo&feature=youtu.be


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## nbpt100 (Jun 1, 2015)

It sounds like to me you just need to tweak the jet screws. I would give the High screw a 1/8 turn richer (CCW) and see what that does. You may have to go more but try it before you rebuild it. If you have limiters on the screws and you cant go further then you need to remove the limiters. People break them off with various methods. The Limiters are a noble Idea that is usually not practical


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