New Ryobi S430 engine dies on full throttle

losrubiosMarch 30, 2009

Just bought a new Ryobi straight shaft 4 Cycle S430 trimmer last weekend at Home Depot to replace my aging 1079r that did 8-9 years stirling service! It starts OK but the engine dies on the way to full throttle. Gas is brand new and my other power tools (mower, chipper/shredder) are running fine on the same gas. Looks like it will be back to HD next weekend for an exchange/refund but wanted to let everyone else know in case you end up with a out of the box $200 lemon like this one - probably a badly adjusted carb or blocked crankcase vent or similar.

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I had the same thing happen to me a couple years ago on a different hand held. I just about reached for the tools when I decided I wasn't employed by the factory and their quality control wasn't my job. I didn't break it down and re-box it, just took it back like it was.

    Bookmark   March 30, 2009 at 9:56PM
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I purchased a Ryobi S430 on the 31st of March from Home Depot and I had the same issue. I returned the trimmer this morning and exchanged it for another one. When I spoke with the power tools "expert" at Home Depot this morning and he suggested that I should not prime the engine 7 times as indicated and only prime it until I see fuel in the bulb. I did just that and still have the same issue. There must be some design issue with the throttle/choke. I can manually hold the start/run level half way and the engine will run at full throttle.

    Bookmark   April 3, 2009 at 8:34PM
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Here's the end of the s430 saga. I took the new one that wouldn't run at full throttle without dying back to Home Depot and exchanged it for another s430. Got it home, when it started up it was misfiring when I first started it after assembly. After about 5 mins the misfire went away. I used it for about an hour and then crankcase oil started leaking out of the air filter (quite a lot) and the misfire came back. The replacement would run at full throttle but developed a misfire which was more like a hiccup where the engine stopped and then immediately fired again. This was quite uncomfortable as it rotates the trimmer in my hand when it refires again.
So off I went back to Home Depot, and got a refund. Ryobi, if you read these forums about your products, go back to the drawing board with the s430 as they're junk.
I went off to Lowe's and bought a Troy Bilt 4 Cycle. It has about 1cc less on the engine and 1" less on the cutting swatch but most importantly it works.

I would strongly recommend against buying the current Roybi s430 model and that probably goes for the c430 model too since they both have the same motor.


    Bookmark   April 11, 2009 at 12:47PM
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I tied a small electric strap around the choke so it won't close all the way. Works like a champ. My 875R had the same issue but you could adjust the choke manually. Lasted 10 years. Thought I might try a foam filter under the plastic cover. Not sure about that one

    Bookmark   May 29, 2009 at 7:40AM
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My S430 has oil sputtering from the PCV(?) tube that is located within the same black plastic housing as the carburetor air intake causing oil leaks from under the housing. The carburetor air intake also sucks up some of the oil causing misfires, and smoke from the exhaust. Anyone else have this problem or a solution? The crankcase oil level is okay and not overfilled.

    Bookmark   May 2, 2010 at 11:05PM
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Similar experience with the C430. Dies at full throttle. Took it to a local person for repair. He told me the C430 was junk; no air filter, no choke adjustment and leaks like a sieve. Very disappointed in Ryobi; bought this trimmer based on success of power hand tools. Will replace it with Stihl or Echo.

    Bookmark   June 22, 2010 at 11:52AM
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I have the same problem only a year latter I suspose my lost but I will never buy another one from Home Depot.

    Bookmark   April 8, 2011 at 8:15PM
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For what it is worth, I also own a couple of these Ryobi c430 four cycle trimmers. (I picked them up at a garage sale, the owner saying that they would not run at full throttle). And indeed, when at the home shop, both would start but not run at full throttle. It's sad, but nowadays one has to know some of the secret handshakes to get trimmer motors to run properly, as the carbs are set to pass emission requirements. Also, owners are well advised to purchase the necessary "secret" carb adjusting tools. See ebay for that. Happily, I already had the proper carb adjustment tool, and also happily, the carb on the c430 is adjustable. Once the carb air/fuel ratios were adjusted for proper running (not emissions), both of the trimmers run great. I also changed out the crankcase oil (thin grey stuff) with automotive 15w40. Don't overfill. I use one as a string trimmer, and another as an edger. The edger works REALLY hard, and is humming along fine. It is sad that consumers are challenged by these barely running small engines. If anyone wants more details on adjusting the carbs on these, just ping back and I will post more details.

1 Like    Bookmark   May 6, 2011 at 6:41AM
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Docdavid, please post more details for adjusting the the carbs on the Ryobi c430 trimmer. Thanks!

    Bookmark   May 6, 2011 at 1:17PM
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OK, here are some of the particulars: First let me say that I still haven't figured out why these trimmers don't have an actual air filter. Maybe more on that later.

Second, to adjust the carb, you must first acquire the proper tool. I found my set of carb tools on ebay from the vendor: Randy's Engine Repair. I got a set of four, but you could order just the one you desire. (No connection with this vendor, other than a very satisfied customer) You'll need the "pac man" tool to fit the Ryobi carb adjustment screws.

The instructions below assume that you have a functional carb and an engine that has compression and spark. Fresh clean gasoline, no broken fuel lines, etc.

Tool in hand, remove the carb intake cover. The high and low adjustment needle screws are viewed looking at the carb from the shaft end of the motor. They are round and black. Fit the tool over the spline of one of the needle screws and turn in the screw clockwise until seated. Be gentle--just finger pressure. Now turn out the needle one and one half turn. Do the same to the other screw. Now you have a starting place.

Parenthetically, here is where small engines differ profoundly from the computer controlled engines we generally use, like those now found in cars. In small engines. purely mechanical settings control air/fuel ratio. The owner of said small engine has to take control to achieve the proper air/fuel ratio. It's stoichiometry!..

But back to the trimmer.....

Leaving the air intake cover off,

Start the trimmer (using the choke lever and starting instructions as noted on the start label). Here is where the art work begins. You are going for a well running engine that idles well, and has full power when working under full throttle. You will need to experiment with carb settings. One of the needle screws influences idle performance mainly, and the other is mainly for full throttle performance. However each jet influences the other. Engine running, at idle, adjust the low rpm jet to slightly lean (turn clockwise until you hear loss of rpm) then back out the screw a bit, say one quarter turn. Now test full throttle. Squeeze the throttle control. If the engine dies (the main problem with these trimmers) it is still probably too lean so open (counter clockwise) the H needle one quarter turn. Try again. Etc. Adjust the high speed needle for good performance. Basically you are trying for highest rpm, but a bit richer, say one quarter turn counter clockwise.

To find out which screw is idle or full throttle, do some experimentation. When you get the motor to idle, just fiddle with one needle, then the other. By fiddle I mean slowly open or close the needle. The one that causes the most immediate changes in the idle rpm is the L or low speed jet, and the other is the H or high speed jet.

At some point I may get my lazy back side out to the garage and make some videos of this kind of stuff and post them on youtube.

I hope this is helpful to those struggling with these trimmer motors. The above principles apply to four and two stroke engines. The basic problem is that emissions regulations force the manufacturers to adjust the air/fuel ratio very lean, which leads to poor running and, in the case of many engines, high temperature running and engine seizure. And then you have the issues with higher and higher ethanol content in fuel.

Let me know if this is helpful. Or any other questions on these little trimmers.

    Bookmark   May 7, 2011 at 1:11PM
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same here! Should have went with a 2 stroke. I cant even get it started now

    Bookmark   June 5, 2011 at 7:50PM
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    Bookmark   June 5, 2011 at 11:01PM
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In response to willyk's post about the oil leak. I am having the exact issue. I drained the oil and refilled with Ryobi oil but problem persists.

Oil is not overfilled. Unit has less than 5 hours of total use in the last year.

    Bookmark   June 30, 2011 at 3:06PM
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Can't believe this problem continues with what seems like zero concern by Ryobi.
I did find that if I make sure the gas cap vent is cleaned before every use the problem seems to be cleared.
Good luck.

    Bookmark   August 7, 2011 at 6:22PM
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Maybe it is Ryobi's method of keeping under the air pollution limits! After all--a non-running engine doesn't pollute! And a low revving engine pollutes much less than a fast runner! Simple explanation, eh? It is a wonder none of the other gurus here had thought of that!

    Bookmark   August 14, 2011 at 1:16PM
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docdavidb is on the money. I had the same problem, bought the tool, followed the instructions exactly. Within 5 minutes, this thing is purring like a kitten. While it's a shame that these things aren't properly adjusted from the factory, they're great now!

    Bookmark   February 13, 2012 at 2:33PM
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I will second that! I purchased a refurb S430 and have been suffering with poor performance for about a year. After reading this post, I made the carb adjustment and it runs great!

Couple of notes for the less mechanically inclined:
1. The carb intake cover is the piece of plastic with the run/start instructions printed on it. It will pop off with no tools required.
2. The High/Low adjustments are labeled- if you looks very closely you can see 'L' and 'H'.

Thanks for the tip docdavidb!

    Bookmark   March 24, 2012 at 1:22PM
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Hello, I'm glad to see this problem is still current. Well, not glad but it does help since I just got a C430 with the same symptoms. I'll post photos after I finish the disassembly but I think the needle adjustments may be all I need, so far it is spotless internally.

    Bookmark   March 25, 2012 at 1:21PM
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OK, thanks to help from here and elsewhere on the web, I now have a functioning Ryobi. The link is the photos I took during the adjustment. I'm too cheap to buy the special tool so I just cut slots in the screw heads.

One other tip I found. Once you set the choke lever, you can open it slightly and still have the throttle set on the fast idle speed cam. Don't know if this was intentional from Ryobi as it's not listed in the instructions. It helps when restarting a warm engine.

Here is a link that might be useful: Ryobi carb adjustments

    Bookmark   March 26, 2012 at 1:41PM
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Sorry to bring up an old thread, but I was just given a c430 (curved shaft version) with some attachments. I'm a new home owner and cash is tight. My friend said the carb was bad, so took it apart and rebuilt the carb.

I cleaned the lines and changed the plug.

This will start and idle fine choked. Will purr like a kitten when the throttle is pulled, but as soon as the throttle is let go it dies. I put the choke on and it starts right back. Pull the throttle and away she goes. Let go and it dies.

I've tried adjusting the carb to no avail.

I've pulled the muffler and cleaned it as well.

Any other suggestion on how to get this thing to run with choke open.

Thanks in advance

    Bookmark   April 16, 2012 at 3:47PM
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I am not having the engine die at full throttle yet, but what I have encountered is: the other day I went to pull the string to start and noticed I was not turning the engine to start it. I removed the shrouds to access and noticed the drive belt had slipped off the upper crank, I reinstalled the belt and tried to pull again, after 2 or 3 pulls the belt has slipped off again-repeatedly. I have opened the unit up completely to try and find some type of tensioner for the belt but cannot-has anyone encountered this problem or can anyone assist. Thanks

    Bookmark   September 26, 2012 at 4:31PM
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I had the same problem of lost power at full throttle after the engine is run-in for a few hours. It was a pain (and expense) to try to get the pacman tool and my carb seems to have only one pacman screw head. Also, I am using the tool on a small island where bush-mechanics applies. I found by losing the warranty, I could make a thin hacksaw cut across the top of the screw (see photo showing 1/4 turn open) and adjust it with a regular small screwdriver.

    Bookmark   May 6, 2013 at 5:04PM
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OK, now I read through all the postings and saw someone else already had the idea of saw-cuts in the screw heads to bypass the special adjustment tool. From the photo in that posting, my unit has a different carburetor as it only has one adjustment screw. Perhaps it is the "Canada" model?

    Bookmark   May 7, 2013 at 12:08PM
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you should probably have a certified tec take a look at it with the proper tools, trying to adjust the carb you self could in up in a lean seize which is not warranty, or running way to rich, with cause excessive carbon build up, also if you cut the slot wrong and can not get a tool on the adjustment, your screwed and need a new carb, plus most likey it has a ruining carb wich has no internal parts availabe but if yoju know so who has experiece with zama carb they can find you a kit but finding someone who is willing to help you is a different story

    Bookmark   May 23, 2013 at 8:50PM
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I am new here, but wanted to post my results. docdavidb is correct in his posting on fine tuning the carb. As far as cutting the needle/screw heads, the carb block is aluminum and the needles are brass, so no worries for sparks above the gas tank. i used a dremel w/ a metal disk, it notches the alum. good for referrence points and gives the heads access w/ a slotted driver. Tuning the carb is much like a 4wheeler or and old VW, yep showing my age.One thing not mentioned is the idle adjustment screw, the larger silver screw w/ the cone shaped end, above the carb. I backed this out until the plate attached to the trigger cable was no longer touching, pulled the trigger and let it snap back. Then I turned it back in until it just touched the plate, and then adjusted in and out, about 2 and 1/4 turns, produced a good idle for me That being said, 1 and 1/2 turns for the high/low screws is a good starting point. Low is on the the left as you look up the shaft to the engine, high on the right. I ended up with about 3 turns out, from seated all the way in on the low, and about 1 and 3/4 turns on the high. I cut my trimmer line for testing, but after it was running well, I extended the line. I tested in heavy brush and it bogged a bit, so i turned the high screw in 1/4 turn. Much better. One note of advice, as we move away from things that are actually adjustable, and we can't even work on or own tool anymore... If you come across screws, needle valves etc, after you've turned them all the way in, make a mark, and as you back it out, repeat this mantra as you turn, 1/2 then 1... 1/2 then 2...1/2 then 3...etc. This is why all needle valves/ screws were origionally slotted. Make notes, if you adjust 1/4 or 1/8 turns in or out, if you ever have to completely disassemble a carb, it is a good starting point. I will post a pict of my carb if I can get a heads up on how in this forum. Good Luck.

This post was edited by sranke on Thu, Jul 18, 13 at 21:17

    Bookmark   July 18, 2013 at 9:05PM
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Well today, after reading this forum. I took out my one year old c430 and decided to get the dremmel after it. I carefully cut a slot into the top of the adjuster, being careful to not cut too deep into the carb housing. I used the thin grinding/cutting disk. Now a regular screwdriver turns it just fine for free. No need to buy some extra tool. Now I have it adjusted and it runs rather well. I seem to have the same carb as radio does.

    Bookmark   March 12, 2014 at 3:13PM
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I bought a 2011 c430 that would not keep running.
Replaced spark plug which was found finger- tight.
Changed the oil.
Replaced the fuel lines and filter.
Adjusted the lifters (metal cam shaft)
Dremmeled the carb screw slot.
Adjusted the only carb mix screw. Tightened all torx screws.
The valve cover and oil pan screws were all loose.
Now it starts on the first pull and doesn't smoke at all.
Not bad for $10!

Next day, ran through 3 tanks of gas. Cold start after 3 pulls and only one pull when warm.

This post was edited by tonyski on Sat, May 24, 14 at 17:54

    Bookmark   May 23, 2014 at 3:09PM
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losrubios: (C430 spits out oil) my mom bought a sears (rebranded Ryobi 4cycle) it had many problems all around burning, leaking oil. (after problem 4, she got her money back) so losrubios, you are not alone.

I went to a sears repair site to get a fridge water filter and noticed they had 6 of them hanging on the wall - refurbished for sale.
That model obviously was a lemon.

    Bookmark   May 27, 2014 at 12:58AM
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Radio I borrowed your photo to show as an example.

Ryobi uses what is known as a Pac-Man screws for carb adjustments. Other types from different brands of power equipment include Single D, Double D, Spline and D Spline.

Dealer are not "legally" allowed to sell carb adjusting tools to the public. I was able to pick up a complete set years ago for around $10.00 before the ban kicked in. You can still find them for sell on the web but they fetch a good penny now days. But you can get them.

I have ground slots into older equipment to adjust the carb. But when it comes to something under warranty I use the proper tools. For if you take something in for warranty work or exchange and they spot that the carb adjustment screws have been "hacked" they can refuse to replace or honor any warranty on the machine.

This post was edited by hippy on Tue, May 27, 14 at 17:58

    Bookmark   May 27, 2014 at 5:56PM
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After 5 tanks of gas it still starts on the second pull, but now it seems to be bound up somehow. While running it just slowed down and came to a stop. starts fine but something is preventing it from running

The lifter post came loose. Tightened it back down, adjusted lifter and all is well.

From the manual...While holding a wrench on the flats of the adjusting nut with one hand, loosen the retaining nut with a second wrench as shown. Take care not to loosen the stud.

This post was edited by tonyski on Mon, Jun 2, 14 at 14:59

    Bookmark   May 30, 2014 at 2:05PM
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Mine was running so erratically till I read this thread. I loosened the air intake/filter housing and used my dremel to cut a slot in the carb screw turned it a quarter of a turn and after tightening it all up "boom" it starts first pull and keeps going.
Thanks for the help it was driving me mad

    Bookmark   June 15, 2014 at 1:50AM
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The post docdavidb put out there really helped me with adjusting the carb. But the trouble I continue to have is I can only keep full throttle if I take the filter out. I've tried cleaning but as soon as I put filter back in I only get about 3/4 throttle. Any ideas?

    Bookmark   last Saturday at 1:53PM
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