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I have an otherwise pretty nice Husqvarna 2 cycle gas weed wacker. AKA Trimmer. It's about 5 years old. It has two problems, which I'm sure are the same problem. And it's had them since it was new. Rather than fighting with this thing every week, I really should just fix it.

Symptom 1:
It dies if you let it idle. It will run with the choke partially on but with the choke fully off, it will slow down and usually in a few seconds to a minute, it conks out. It seems to die faster when it's fully warmed up, than when it's cold.

Symptom 2:
If it is idling or close to it, and you pull the trigger to rev it up to operating RPM, it will bog down and potentially stall out if you pull the trigger too fast. If you raise the RPM slowly, it gets up to speed and then it can handle the higher RPMs just fine.

I do NOT think my problem is that I need an idle screw adjustment. I think my problem is that the air/fuel mix is off. But I'm not sure if that can be adjusted, or how it can be adjusted. It's been doing this since it was brand new, and it still otherwise runs like it's new. So I don't think it's being caused by any other typical "old engine" problems.

But I'm no mechanic so maybe I'm totally wrong.
Also note, I've always run it with 1 ounce of seafoam in the gallon of oil gas mix. So I would expect the insides of the engine to be very clean.

So what do you think?

It is rich on the idle jet
A lot of hand helds are supplied like that and need to be retuned when run in .

most of those two cycle carbs have a life span of just a couple years. Learn how to rebuild it or replace it. The diaphragms in it that control fuel delivery stretch and go bad. I have found that draining the tank and running the device dry after each use doubles the life but even so the carbs go bad with the symptoms you describe.

But this isn't a new problem its had since it got old. It's been like this since day one.

l008com said:

But this isn't a new problem its had since it got old. It's been like this since day one.

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My question is why have you put up with this for five years? Sounds like a simple carburetor adjustment. OEM carburetors will last for several years. I still have the original in my Stihl FS250R and have only replaced the metering diaphragm once.

On a 5 YO trimmer, just get a carb rebuild kit or new OEM carb. The diaphram is probably "hard as a carp". Taryl

Boy a lot of techs with no idea of what is wrong. The closest is Slomo and Tiger a close second.

It not tuned rich but is on the lean side; hence, the reason it runs better with a little choke. And as the rubber metering diaphragm ages it does stiffen up over time and I have seem rock hard on non runners. The Mylar fuel pump diaphragms do deform some over time but the rubber diaphragm can not stretch as it is rubber coated cloth.

One thing I do see in new carburetors is that the metering lever is usually set too low which cause the carburetor run lean at full speed as the needle valve can not fully open. And this can idle problems too. On these carbs even a slightly stiffen metering diaphragm can cause problems.

Now the problem is it does take a knowledgeable technician to diagnose and repair these two cycle engines. You must have the proper tools like the mixture adjust tool and and most cases the correct metering lever setting gauge tool. Zama usually the easiest to set as nearly all are set the same but with Walbro there is multiple settings depending the carburetor model which is I got the Zama Z tool and both of the Walbro W tools. For home owner these are expensive for one time use. It also doesn't hurt to have a pressure/vac tester to test the sealing of the carburetor and metering needle sealing plus tach to set the idle and max rpms. Again a shop can justify these as they are repeated used.

And many of these carbs have to be tune slightly rich on idle mixture so you can have a quick acceleration when you pull the throttle lever quickly. IE very little lag getting up off idle speed.

One thing of note if you tune to carb too lean you run the risk of destroying the PNC from lack proper oiling and overheating. Personally I would advise the OP let a professional two cycle tech do the work. I just had to give a customer the bad news that his expensive Stihl is burn up because he let his cousin work on it and he had left the carburetor loose. Costs more now to repair than a new saw but does make a good Stihl boat anchor.

PNC > Piston and Cylinder

One thing of note here is that companies are getting to where they will not sale you a carburetor repair kit but only sale replacement carburetors. More money in their pockets. Stihl is a prime example of these companies. And with Stihl owning Zama many of the repair kit and parts are no longer available so you have to buy replacement carbs. Can't even look up the parts so I can get parts out my stock parts any more. And Walbro site no longer have full carb IPLs as they have gone to kits and carbs only.

I get my kits here: https://www.carbtech21.com/default.asp

Tiger Small Engine said:

My question is why have you put up with this for five years?

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It's very easy to work around this problem, it's more of an annoyance than a problem. But 5 years is my limit I agree that it sounds like some kind of fuel adjustment issue but beyond that, I don't know how to fix it so I just ignored it.

StarTech said:

Personally I would advise the OP let a professional two cycle tech do the work.

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LOL Walk into an engine shop with a 2-cycle anything and see what happens. Here's a hint, "we don't work on those, throw it away and buy a new one" is what you get. Others say right on their website "NO LONGER SERVICE BLOWERS OR STRING TRIMMERS". I've never found any shop anywhere near me that will work on 2 cycle engines. I had two different very problematic chainsaws over the years and after searching high and low, I gave up.

But this trimmer is a different situation. Its a good brand and a good machine that, aside from this problem, runs great and always has. It's certainly worth fixing. Especially if it's just a matter of taking off the air box and adjusting a screw. I don't think the problem is that the carb itself has gone bad. And I base that on the fact that it's had the exact same problem since it was brand new, and it's never gotten any worse.

I added a few pictures of the machine to the original post. I also downloaded it's owners manual but nothing about carb adjustments beyond the idle speed screw. I haven't had time to take the machine apart more and actually get to the carb and see what it has for other adjustment screws. Seems like I'm always in a huge rush on yardwork day.

OK I just found this video on youtube and that seems to be right on the money:

But the shot of the driver is very blurry, anyone know what it actually looks like? Is it just a socket?

l008com said:

LOL Walk into an engine shop with a 2-cycle anything and see what happens. Here's a hint, "we don't work on those, throw it away and buy a new one" is what you get. Others say right on their website "NO LONGER SERVICE BLOWERS OR STRING TRIMMERS". I've never found any shop anywhere near me that will work on 2 cycle engines. I had two different very problematic chainsaws over the years and after searching high and low, I gave up.

But this trimmer is a different situation. Its a good brand and a good machine that, aside from this problem, runs great and always has. It's certainly worth fixing. Especially if it's just a matter of taking off the air box and adjusting a screw. I don't think the problem is that the carb itself has gone bad. And I base that on the fact that it's had the exact same problem since it was brand new, and it's never gotten any worse.

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Goes like this
I charge $ 72/hr (Aus)
To just pressure test the fuel tank , carb & crankcase to check got air leaks is 45 minutes ( $ 54 )
If the diaphragms are cactus there is another 1/2 hour + parts so we are now over $ 100
Then there is carb adjustments easy another 1/2 so we are getting close to $ 200
After that it is do my trimming around the workshop, I like to run a full tank through it because I want it to fail here not after the customer took it home
Add to that time ( not billed for ) to do exactly what Star said , try to find out what kit was needed and tuning sequences as some of them are rediculously complicated .
Now in the same 3+ hours I could have done a full service on a ride on for around $ 500 or played silly buggers with this trimmer for $ 200, assuming that of course I have the required parts in stock and they don't have to be ordered in .
And funny enough earlier this season I did 122LD which the 128 Replaced , probably spent the entire day on it, got it running beautifully & sent it back.
Two weeks later it was back in the shop , was sure the customer had been fiddling with it as the carb setting were way out ( I record them in my diary , the factory recommendations & what they ended up bing )
So I readjusted it , ran 2 tanks through it and a fortnight it was back again with the carb way out of adjustment .
Then I twigged that the needles were too easy to turn
Tried a new set, still too loose so it was a dab of Lock Tite, adjust the carb again, leave it a day then test again ( got 750 yards of fence line done if nothing else )
That was 3 months ago & customer is happy with it , but with 2 lots of free warranty work there would have been better than 20 hours for $ 200, I would make double that working at McDonalds flipping burgers .
That is why shops are reluctant to work on them , because we loose money
Ryobi trimmers start at $ 50 NEW
Husqvarna & Stihl start around $ 100
Hondas @ $ 450 I will fix all day and the bulk of my commercial customers use Honda or Honda powered trimmers

l008com said:

OK I just found this video on youtube and that seems to be right on the money:

But the shot of the driver is very blurry, anyone know what it actually looks like? Is it just a socket?

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It is a spline ( 17 tooth from memory )
I have boxes full of carb tools because they bring a new one out every week and as it is illegal to sell them even to workshops , I have to buy a new set from China via Alibaba several times a year
Another reason why workshops do not want to work on them .
We are supposed to have both a CO/CO2 meter + a hydrocarbon meter and hook these up to the exhaust when tuning these engines ( fines if you do not )
FWIW below is the tune up proceedure , week at least for this week because they keep on changing them
There is a Husqvana tool number for the clutch tool pop it into Scammazon for an illegal kit purchase ( and they wonder why we think all this stuff is a joke )

sgkent said:

I get my kits here: https://www.carbtech21.com/default.asp

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I wondered how long it would take for some one in the USA to start flogging CTS stuff now that Dave in HK seems to have vanished .
Just be careful because CTS do not use all the same shape codes that Zama & Walbro do so some of the parts in the kits will look different .
Apparently there is some patient problems with some ( not all ) of the diaphragms , well that is what they told me anyway .

bertsmobile1 said:

Then there is carb adjustments easy another 1/2 so we are getting close to $ 200

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To clarify, I wasn't questioning the economics of whether shops should or shouldn't work on tiny motors. More just starting the fact that none or almost none do. I haven't found any that do. Thus the suggestion to bring it to a pro was a little silly. But given everything I've read, it sounds like a simple twist of one of these screws is all mine needs.

Regarding which size driver I need, mine is definitely a 21 tooth. I took a high res photo, zoomed way the F in, and counted in Adobe Illustrator using some polygon tools to make sure I wasn't missing anything

it is a carb problem if it is a five year old problem. None of those 2-cycle things were made as anything more than throw away unless you learn how to repair them. Example - 2 cycle Homelite marketed as Ryobi hedger - muffler cracked and rotted away in a couple years. Carb went bad. Fuel tank hoses rotted. Fuel cap went bad. Shall I go on? I repair mine but frankly it isn't a lot cheaper than buying a new one every 5 years.

l008com said:

To clarify, I wasn't questioning the economics of whether shops should or shouldn't work on tiny motors. More just starting the fact that none or almost none do. I haven't found any that do. Thus the suggestion to bring it to a pro was a little silly. But given everything I've read, it sounds like a simple twist of one of these screws is all mine needs.

Regarding which size driver I need, mine is definitely a 21 tooth. I took a high res photo, zoomed way the F in, and counted in Adobe Illustrator using some polygon tools to make sure I wasn't missing anything

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And I was trying to explain why shops don't do saws any more unless you bought it from them.
Chain saws, blowers & line trimmers are all loss making repairs
Push mowers are not all that much better either .
Since there are no more phone books it is hard to find genuine repair workshops because the search engine will always direct you to the most popular site or the ones that pay good money to pretend to be the most popular so you have to do more searching other then face book & google to find them or you will just keep on finding glass fronts .
Glass fronts only want to sell new products because there is a 50% retail mark up on most lawn gear and the shops are all owned by big businesses so run by accountants .
I sent you the manual there is not much more that I can do
I do not sell any whole goods
I just do repairs
But you will not be able to find me electronically
I have a display add in the local free newspaper and a business card at the 3 local shops notice boards
That generates more work than I can do
It is mid winter right now & have 6 months of work already booked in .