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Grass Trimmers

Mend Mend Garden Tools, Grass Trimmers

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

My unit will idle but when you give yhe gass it dies. I have replaced the spark plug, feul lines, feul filter, pulled the carb and cleaned it and the feul bulb of all trash. pulled and cleaned the oil resevior and the vent tube. checked the one way valve going to the intake. Replaced the foam air filter. and it still starts easy but when I pull the trigger for acceleration the thing dies. This happens no matter where I have the choke set.

Henry Helaune
June 2005
in mine there was a screw on the side of cab. looks like a plug if loosened gas comes out. turned it loose and let some gas out tightened it up and the thing ran like new. must have been a bit of crud in there some place.

December 2012
Throttle cable has come out of its slot on rotary throttle control on carburetor. You may have to rotate the rotary throttle control 180 degrees since there is a compartment on the rotary control only on one side for the cylindrical slug that is on the cable.

I know this by experience. Engine will only run at idle with throttle cable in this condition.

April 2010
ensure that you don't have a primer bulb leak/crack. Recently had the same symptoms and noted whn I placed my thumb over the end of teh buld the trimmer would continue to run fine but when I took my thumb ff it'd die. After pressing teh primer bu,b more I began to get a small stream of gas shooting out whenever I started it up.

October 2009
Mark's answer (May 2007) referencing adjusting valves on a "hot" running engine is right on the money.

September 2008
I have the same problem every year. It was the valve adjustment. Look at the last section of the owners manual and they show how to gap the valves. You'll need a feeler gage and a socket or box wrench.
Take off the plastic cover (3 screws), You'll need a Torx for the rear one, and also to remove the valve cover screw. Be careful lifting the valve cover to try and keep the gasket intact.
Remove the spark plug and then slowly pull the starter cord to make sure the valve you are adjusting is fully closed. You can tell by looking at the other valve to see that it's fully open or pressed down.
Use your feeler gage between the rocker arm and valve stem and there is probably a lot of play. Gently tighten the nut in the center of the rocker arm a little at a time, moving the feeler gage until there is a bit of "pinch".
Then pull the starter enough to get the other valve fully closed and do the same.
You can try and start it with the valve cover off to see if your adjustment worked.
Once I get the feeler gage setting to get me in the ballpark, I start it up and warm the engine a bit, then at full throttle and using a 1/4" drive socket, I'll tweak the adjustment nuts tight or loose. The engine will start to die if I go too much either way so I find the point where the engine goes as fast as possible. I do the same with the other valve, put a drop of locktite at the top of the nut and put it all back together.
After about 8 years, the exhaust valve spring is relaxing and not fully closing the valve. I found springs online for $3.27 each. Pretty cheap to keep it running.
Good luck!

May 2007
my gas tank supply hose had a crack in it. it was supplying just enough gas to run at idle, but at higher speed it would not supply enough gas and would die. I am in the process of searching for a replacement gas tank supply hose.

James Barber
September 2006
Mine would start, and run at idle but once I tried to speed it up, it would just die. It seemed to just run out of gas. It would idle for ever though. After looking into almost everything, I found the carb. was plugged with a very small wad of something. I had to take the entire carb apart to find it. Since then it runs great. Don't mess too much with the idle screws - that's not the problem unless you've changed them.

John Harrington
May 2006
replace carb diaphram (rebuild kit 10 bucks)
they get stiff with age and alcohol in gas
soak dissassemled carb in paint thinner
more info at joseph_dudek@bellsouth. net

joe dudek
April 2006
have you move the two screws on top of the carb.(the ones with springs around) Sounds like your engine is getting flooded. try turning the screw which is futherest away from the fuel tank anti clockwise about a half turn.

January 2006
My ryobi 875r is exhibiting the same symptoms after it stalled while I was using it this afternoon. Did you resolve your issue?

Have you had any problems with your clutch or upper shaft assembly. I replace my upper shaft a couple of months ago and I have the feeling this is related to a problem with the clutch. Does this model Ryobi have an automatic cutoff if the clutch does not engage?

October 2005

September 2005


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