Ryobi 2-cycle Trimmer Problem

[cruzenmike]

I have a 26cc Ryobi 2-cycle string trimmer that is giving me some problems. The model number is RY28040 and it is a half crank model. The problem that I am having is that all of a sudden it is hard to start and it keeps surging and wanting to stall like it is starving of fuel. Choke is working properly and open all the way after warmed up. Fuel line is full with no air bubbles. Last year I replaced the spark plug, fuel line, primer line, primer bulb and fuel filter. The gas if fresh ethanol free with Echo red max 2-cycle oil mixed at the proper 40:1 ratio. Before I start getting into tearing it apart, I was hoping that one of the experts on here could point me at what to look at first. I certainly do not have an issue with simply replacing the carb since it is so inexpensive, but what I am hoping is that the problem is not more "mechanical" and that there isn't some catastrophic failure impending.

I had considered just replacing the power head since I have all of the Expand-It attachments, but I have not found one that I like and the replacement "full crank" Ryobi power head just doesn't spool up fast enough or rev high enough for my liking.

Alternative is to just replace the whole line with the Honda 4-cycle system, 35cc power head and attachments. But if this unit is still capable of working I would like to keep it a while longer.

Thanks in advance!

 

[bertsmobile1]

The carb has an internal fuel filter screen that can get clogged.
So it will either be a carb problem or a fuel tank seal / vent problem
The fuel tank must be pressure tight to between 7 to 10 psi
It also has to allow air to get in or fuel can not get out.
Fuel lines come in 2 types, thin wall , return tube and heavy wall suction tube
Lots of shysters by a 500' roll of the thin wall tube because it is cheaper then cut it to length, put it in a plastic bag & sell it as a rebuild kit with a filter & gasket at around a 2000% mark up on ebay, craigs & amazon.

The 1/2 crank engines are also prone to leaking at the crank case gasket and the crank case sealing plate doubles as the fuel tank mount so if you loosened it to get the tank out then the gasket should be replaced.

 

[tom3]

About a 1 in a hundred shot here but I just got into this with my blower. Figured to junk it and get a new one, they are pretty disposable. Turns out the spark plug had a really fine piece of carbon between the center and ground electrode. Barely could see it. Would start and run about like you describe. But then I'd start with a different plug.

 

[cruzenmike]

Thanks for the help guys. I will pop he spark plug out, clean, gap and put back in. I will also pull the carb apart and check the screen. I have seen these get coagulated (in my Ryobi handheld blower) but in that case it wouldn't run at all. Either way, it sounds like it might not be that bad or too costly to fix. I will report back and let you know what comes of it.

 

[bertsmobile1]

If you pull he carb apart, fit new gaskets because the old ones will have both gone hard and distorted.
A gasket & diaphragm kit is not much less than a replacement carb
Starting to sound like a nursery song about a bucket with a hole in it Dear Henery ?
Over time the metering chamber diaphragm goes hard and that makes acceleration sluggish.

A partially blocked muffler does the same thing & may prevent the engine attaining full speed.
A leaking fuel tank can also reduce the speed that the fuel gets into the carb which will also make the engine sluggish to accelerate & may prevent the engine getting to full speed.

 

[cruzenmike]

I want to say that I replace the carburetor on this may be 2 years ago. The unit itself is about 10 years old. The gas tank does not leak that I'm aware of and the gas cap was replaced last year. as for the muffler I am not really sure if there's any type of obstruction but I could always pop that off and see if there's anything visible that could be in the way. But I am starting to think that it is in the carburetor itself because I was noticing before this week that when I would initially pull the throttle trigger it would want to bog a little bit and then it would speed up so I was having to feather the throttle to get it up to speed. And then all the sudden it got to the point where it just wants to die or surge.

 

[bertsmobile1]

That is what happens when the H & L jets get out of wack.
Can bee crud in the carb, stuck check valve or one jet adjusted wrong

 

[cruzenmike]

So, I took part of the trimmer apart and looked at the carburetor and spark plug. Please see the attached pictures. While I do not think the spark plug to be bad, and the diaphragm to be fine, I did notice that there was gas all over the outside of the carb and in the air cleaner area. Both fuel lines were nice and tight and I did not see a leak there. There could have been a leak from the plate holding the primer bulb but I do not understand why this would cause hard starting, surging and stalling. I did not see anything else out of the ordinary with the trimmer. Looked through the intake and could see the piston moving up and down with only slight signs of wear.

I have found a cheap aftermarket tuneup kit that includes a carburetor, fuel lines, spark plug, fuel filter and gaskets for $13 https://www.ebay.com/itm/Carburetor...348118?hash=item48c47fb156:g:tcoAAOSwrhNckIoh . I figure I will give it a try. The only question that I have is, what kind of tool is used to make adjustments to the high and low sides on the carburetor?

 

[bertsmobile1]

Do you know what a stiff diaphragm looks like ? cause I don't .
The internal filter is under the metering needle and is accessed from the other side of the carb.

 

[cruzenmike]

Well, I have the trimmer running again. I purchased a kit for $12 on eBay that contained a carburetor, spark plug and fuel filter. I went ahead and put some anti-seize on the spark plug and boot protector on the wire and put that back together. Then I replaced the fuel filter and installed the new carburetor. I would like to say that it worked perfectly after that but it didn't. I am glad that I purchased the PAC-MAN tool to adjust the low and high jets on the carb. I started messing with the adjustments on the carb until I got it where it is just above an idle when off the throttle and it revs both quickly and smoothly to the top RPM. In hindsight, I would have probably only needed the tool to adjust the carb that was in it to smooth out my throttle and fix the stalling issue. With that being said, I cleaned up the old carburetor, put it back together and have it sitting on the shelf for it I need it.

The last thing that I will mention is that the carburetor that I purchased is not identical to the one that I had. The main difference is that on the bottom end of the choke and throttle shafts is a spring return mechanism. Basically when you pull the throttle it resets the choke to open. I had replaced the carburetor on this trimmer before so I cannot remember what the original looked like, but I am quite certain that the newest one is not correct. The starting instructions for my specific trimmer has you hold the throttle trigger down while it is either at full or half choke. I cannot do this with the new carburetor but thankfully it is starting choke on and throttle untouched.