What's wrong with my Ryobi string trimmers?

keboApril 18, 2010

I have two Ryobi string trimmers, one is the older 790r model, and the other one is newer but not sure which model it is. They both essentially have the same issue... They crank up easy, will sit there and idle just fine, but once you try and give them any throttle they just want to die like you hit the kill switch. I had a suggestion on another forum to check the spark screen, so today I pulled the muffler off of the 790r and checked it. Well, it had no screen, and there was no clogging of the exhaust port either. So, any idea's what's wrong with these two trimmers? Thanks!

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masiman(z7 VA)

Check the air filter, could be that you are not getting enough air for the increased gas.

    Bookmark   April 18, 2010 at 8:41PM
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Try close the choke and rev the engine and see whether that help. If so, something is causing it to run to lean. That could be a clog gas filter or carb problem. Change to a new gas filter.

Check also the two lines going from gas tank to the engine make sure there is no crack.

If that don't help, try run some SeaFoam mix and see whether it help after a tankful of gas. 2oz into one gallon of gas. Use fresh gas. Also try loosen the gas cap to see whether that help.

If none of those help, you might have more serious problem. Don't think of it until you try all the above first and come back and update. We'll go from there.

    Bookmark   April 18, 2010 at 10:22PM
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Thanks for the replies so far. I didn't mention it in my OP but I actually tried running the 790r without the foam airfilter. I noticed it was soaked with gas/oil mix and I thought that might be the cause. It did run a little better with the filter off, but it didn't solve the problem of cutting off when you give it some throttle.

I will try the suggestions by yungman and let you know the results.

    Bookmark   April 18, 2010 at 10:52PM
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Put the filter back before you really kill the engine!!! It is not too bad to have the foam wet. Happened on some of my stuff. Some engine require you to wet the foam with oil the get better filtration anyway.

Beside if oil block a little air in your case, it will help if your engine is running too lean.

Is your gas less than two months old? For equipment that is not used regularly, stale gas may be the problem. Try using some SeaFoam in gas. In your case, 2oz in one gallon and run a tankful. It is good for your trimmer no matter what. Unless you finish all your gas within 2 months, use Stabil in your gas to keep it fresh.

    Bookmark   April 19, 2010 at 12:55AM
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masiman(z7 VA)

Running without the air filter is not recommended but if you are careful it will not do significant damage. It will allow more air to flow than with the filter giving a slightly leaner mix but I wouldn't worry about it.

It sounds like you are down to checking your fuel supply. The fuel lines and filter as yungman suggested, but also your carburetor. If you are idling, I'll assume your fuel is decent but new mix wouldn't be bad. How long do they sit between starts (i.e. you don't touch over the winter, etc.).

You could have an air leak that shows itself when you try to give it gas, but I would troubleshoot the fuel supply first.

Others may have different suggestions.

    Bookmark   April 19, 2010 at 7:50AM
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The carb. needs to be adjusted. Turning the high speed adjustment screw slightly (1/8 of a turn) counter-clockwise will probably fix it.

    Bookmark   April 22, 2010 at 12:23AM
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If the fuel lines rotted off then you probably had used corn gas in it which mostly likely done the same thing inside you carb. ruint the diaphram and tarnished up the passages. If all else fails you may have to disassemble the carb. clean out all the passages, buy $8 carb. kit and install it. pay close attention which way the diaphram seal goes.

    Bookmark   April 22, 2010 at 11:32PM
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RYOBI CS30 GAS TRIMMER, starts right up and
idles fine but bogs out at high rpm's. Give me some possilbe causes of this.

Tx Ron

    Bookmark   May 20, 2010 at 4:54PM
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grab the spark plug and wiggle it.
I have seen a few of these engines where the cylinder screws are vibrating loose and will idle but not go to high.

    Bookmark   May 21, 2010 at 5:25PM
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esemilio(Z5 WI)

kibo & lokid - Have you solved the problem? If yes, what was the solution?

    Bookmark   May 24, 2010 at 11:06PM
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Have a rather new 30cc trimmer that doesn't appear to have any ignition. How can I test for spark? With adequate fuel, I don't even get a pop out of repeated pulls.

Are there contact points in the ignition system? What might be bad?

    Bookmark   November 9, 2010 at 7:27AM
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First off you can check for spark by removing the spark plug, plug it back in and lay it onto the metal part of the cylinder jug. Pull the rope and you should see nice blue spark arching.

Now what kind of switch do you have? Does you switch just shut the engine off or do you have two positions on it ON? or OFF?.(you have two wires going to the switch, with the two wires touching it should cut the ignition off and with the two wires seperated you should get ignition, if so the switch is bad?) First thing I would suspect with no spark at the plug would be the cheap switch? You can remove the switch and check it with a mulimeter. it should show conitunity in the off postion cause this it what shut the ignition off by grounding out the coil.

I have the one position switch and my problem was the weed eater would not shut off. The cheap switch would not ground out the coil so I search through my spare parts off junked weedeaters and found a good switch.

I dought your weedeater has points, IMO they started using electronic ignition about 20 years ago?

    Bookmark   November 12, 2010 at 7:08PM
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I a newer ryobi string trimmer from Home Depot. Ran great last year but this year it has a hard time getting up to top rpms. Then once its warm it is almost impossible to star again. What could be my problem? Thank you

    Bookmark   May 15, 2011 at 2:10PM
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Zach: Just a typical Ryobi trimmer. Much like the Weed-eater trimmers that I have very tempermental unless you ensure to winterize properly . You will have to clean the fuel circuits within the carb . I usually remove the jets and clean with carb cleaner and readjust both High and low to 1-1/4 to 1-1/2 turns out from seated. The restriction within the high speed jet is causing the lower rpm at wot position . In the future use stabil or Startron or seafoam fuel additive prior to running you unit dry for storage. Also you should inspect your fuel and air filters if your trimmer is more than a few yrs old . I also normally replace the spark plug every 2-3 yrs , small price for better performance .

    Bookmark   May 15, 2011 at 5:14PM
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I had a similar problem with my John Deere trimmer. It's the ethanol in the gas causing this problem. The ethanol causes tiny particles from the fuel lines and the gaskets in the carburetor to build up in the jets in the carburetor. It's a real nightmare on small engines, since the jets are so tiny. You can try to use some carb & choke cleaner, you might get lucky. If it's really compacted in there, it might be cheaper to buy a new carb and put it on than to fix it. Before you do that, replace the fuel lines. Make sure they are ethanol-ready.

    Bookmark   May 17, 2011 at 1:38PM
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DJ: The ethanol absorbs water or moisture within air (atmosphere) which causes oxidation of metal components and also as you have indicated can cause break down of older small engine carborator and fuel system components. Routinely gum and or varnish is produced which restricts fuel flow . In extreme cases rebuild kits are required but normally you can clean the internal fuel circuits and prevent reoccurrences by using a ethanol designed fuel treatment . I suppose if left long enough you may find a new carburator the only solution , but usually i have been able to clean or refurbish OEM units rather economically without any long term problems .

    Bookmark   May 17, 2011 at 1:56PM
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I had oxidation trouble on my lawnmower. The needle valve that control the flow of gas from the feed into the jets oxidized, and when not running, gas would pour through the cylinder onto the floor until empty. >:o

    Bookmark   May 18, 2011 at 3:03PM
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If there is a finikier gas engine than a Ryobi string edger I don't know what it is. Here's how I finally got mine to run: Break off the plastic California emission limiters on the high and low speed needle valves, take them out clean them with the wire wheel on your grinder. Now you can really tweak the gas flow. Throw away the air filter. I know some one said it will ruin the engine, but what good is it if it doesn't run anyway? If it ruins the engine, throw away the edger! By the way I also removed the fuel filter, leaving only the metal clunk.

Papa Jim

    Bookmark   May 18, 2011 at 3:46PM
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DJ: Exactly what happened to a neighbours old lawnmower. He left it under a tarp one yr and used his new sit down ractor mower. Then the next yr he decides to pull off the tarp and cut the backyard lol . Well the gas was so sour (water contaminated) from thermal cycles (hot and cold) due to mid day sun and colder spring nights . The condensation formed on the walls of the half empty fuel tank and sat in the bottom of the tank. Well you got it , he had to pretty well replace the entire carb , since all the white metal components were covered with oxidation . He stated that thia was th 1st time that he had not winterized the unit roflmao ! However your right in that ethanol really magnifies the oxidation and varnish / sludge issues today . :)

    Bookmark   May 18, 2011 at 5:36PM
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Before you throw out your Ryobi trimmer like I was ready to do today or take it to a repair place, try that Seafoam stuff. I just dumped some into the gas tank and started it up. It totally fixed my issue of it starting, idling but unable to give it more gas. I think that the Seafoam fixes the damage that the ethanol does--going to try in it my lawnmower too and see if it works better.

    Bookmark   June 9, 2012 at 7:15PM
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hello all
i have a ryobi 4 cycle wheeled trimmer, not quite a year old. it cuts good, runs good. it has the push through line head. 2 pieces of line around 12 inches long. i was going to put in new line and one side would not go in like usual. how do i take the head apart without forcing or breaking something. it looks like it will come apart but i dont want force anything and break something. thanks.

    Bookmark   May 24, 2013 at 7:21PM
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