Ryobi RY253SS 2-cycle trimmer dies after about 10 seconds

[RevB]

I have recently experienced the same set of circumstances w/my Ryobi RY251PH strimmer. (Manufactured 10-22-15)
I must have dropped mine as I had a small piece coming off the carburetor with what looked like a ball behind it.
Order the $9 Amazon Chinese flavor of the day and attached.
What I discovered is that it runs at a totally different "richness/choke" setting which we cannot adjust.
Pull a few times with choke on 100%.
Whether it starts or not, then move choke to somewhere around mid setting.
Start it here.
Mine runs BUT if I totally shut choke off so more air goes thru it does exactly like yours.
I think the "richness" setting is off in the ChiComm specials and we can only adjust mixture with the choke setting.
If this works for you, be sure choke is tight so it doesn't vibrate totally open and then die again.
Please advise.
For proof that mine has lasted 10 years as a residential user a photo of manufacturing date sticker is attached.

Hence the need to exactly specify which engine gets the same carb spec as the OEM carb. If you cannot adjust them they are pre jetted for a specific displacement engine.

 

[RevB]

Also just ran across this photo of carb replacement.
Mine had 2 holes, does yours?

Most likely the impulse port for the fuel pump diaphram in the carb body.

 

[RevB]

If you use gas with ethanol in it the carburetor diaphragms are probably shot. You should be using non-ethenol gas. Check that the fuel line and pickup weight in the tank are still intact. This is very common with weed eaters and chain saws. If tgat doesnt fix it, you can buy a new carburetor on ebay, usually for about 20 bucks. Change that and put new fuel lines in it and it should work well for you.

Mostly incorrect . Everything made after the early 80s has switched to materials that are ethanol agnostic as it doesn't do anything to them. Pre Buna-N orings were the common failure and after the switch to Buna-N no more problems. Same holds true with diaphragms.

 

[lbrac]

I've had a ring trapped by carbon in the piston groove cause the piston/cylinder to score when combustion gases pass into the lower end of the engine. Carbon can clog the spark arrestor screen and plug the exhaust. The fuel cap vent can not vent the tank when the fuel is drawn from it, causing a vacuum in the fuel tank when running, or pressurize fuel through the carb into the lower end of the engine when not running and ambient temperature rises. Some carbs have a check ball in a passage in the metering block that can bind due to trash/deposits; it requires a metal cover to be removed to clean the passage. The primer bulb can crack and draw air when the engine is running. Spark plugs can carbon track or crack the ceramic insulator, shorting the spark to ground. And all the various other things previously suggested. Some are easily checked/tested, and others take more effort. Checking the easy ones and ruling them out before moving on to the more elaborate issues is usually best.

 

[TRACTORTOWN]

Remove the spark arrester screen in the muffler. Leave it out. If you can’t remove it, poke big holes in it. Only State that is required to have it is in California. It plugs constantly and does not let the exhaust move freely out of the engine. Most common problem seen on two cycle hand held products.

 

[farmerdave1954]

In can attest from experience that this can definitely be due to a clogged spark arrestor screen in the muffler. My Stihl string trimmer had this issue about 5 years after I bought it new. Took it to the repair shop (due to needing it immediately and simply not having time to work on it my self) and described the problem. The tech just asked if I was going to be using it in a National Forest, to which I replied no. He pulled a pair of pliers out of his pocket, ripped the screen out, handed it back to me and said, "There. You won't have any more problems like that again." He was right. 14 years later the only problem I've had since was a bad kill switch. Never another issue of any kind with it. Even if it's not the arrester screen, pull it out or it will be one of these days.

 

[ttimtucker]

Prior to replacing the carb I had removed the muffler, but that did not change the symptoms. I will definitely keep in mind the spark arrestor as a point of failure for future diagnosis.