My ryobi grass trimmer mod 875r idles but will not run at speed


LawnSite Member
Durham, NC
My unit will idle but when you hit the throttle, it dies. Spark plug, fuel, lines and fuel filter are fine. Cleaned the air filter and the oil. It will start, but when I pull the trigger for acceleration it dies, no matter where I have the choke set.

I did replace my upper shaft assembly a couple of months ago. Could this be a problem with the clutch? Does this model Ryobi have an automatic cutoff if the clutch does not engage?


LawnSite Senior Member
Don't know about any kind of auto cutoff if a clutch is not engaged on any sort of stick machine, but likely you have one of three things going on. A) a plugged air filter B) a plugged exhaust/spark arrestor screen or C) your carb is out of adjustment either running too lean or too rich, starving/flooding the engine. Refer to your manual on adjustment screw settings for your machine and check the exhaust side.


LawnSite Member
Alhambra, Ill.
I have a similar problem. My trimmer will start with the choke on, but it runs roughly, and the instant I engage the throttle, it dies. Where's this spark arrestor I'm reading about, and I can't figure out how to clean the exhaust. Would appreciate anyhelp.:confused:


LawnSite Silver Member
Gas today is a garbage mix. Ethanol in gasoline causes a lot of problems in small engines. Of which, melting plastic lines are the greatest. I'd almost bet that you have a comprised fuel line somewhere. I hope not but sounds like it. There's enough fuel for idle but not for a revved engine. In the future always used ethanol free high test gasoline on any small engine. It's a compression factor.


LawnSite Senior Member
Wichita Ks
In addition to the things already mentioned...

Dump the gas and mix fresh (preferably with no alcohol/ethanol if its available in your area).

Grab the string head (what holds the string and does the trimming), and make sure it turns. If its bound up, you might not have an engine problem. i.e. when it revs and the clutch engages, it can't turn it so, it dies.

Also, the high speed port on the carb could be plugged. You can take the carb apart and spray carb cleaner through all the ports and put it back together. Also you can check ebay for a replacement carb. I got one for my ryobi for around $8 or $9 shipped. But eliminate the other possibilities first.