I am not familiar with the model number but if this is a 2 cycle engine, check the antispark screen in the muffler.

replace your fuel filter and clean the air filter and inspect the fuel lines for cracks.. If that doesn't help,take the carb apart and clean it. I had the same problem on my roybi 775r. turned out to be a dirty carb because I left old gas in it for the winter.

Have the same string trimmer and my unit starts easily, idles well, but will not operate at high enough RPM to cut effectively. The problem is a plugged up muffler. Have cleaned it as best I can several times. Immediately after cleaning the trimmer works very well, but after an hour's use, it begins slowing down at full throttle and eventually will not spin fast enough to cut well. Muffler is the problem, but I do not know of a good way to clean it. Anyone have a good suggestion?

Could it be that your fuel mixture is too rich (say 30:1). With extra oil I would guess that your muffler/spark arrestor could build up carbon more quickly. Or maybe the carburetor is misadjusted?

Last evening I thought I'd give cleaning the muffler one more try, even if it meant damaging the muffler. In the process I inserted a screw driver into the "tail pipe" as a probe, and when I rotated the screw driver I noticed that the flared end of the exhaust moved relative to the muffler body. It did not appear to be a separate piece, but was, and I pulled on it and it came out. On the end of this flared piece was wire mesh in a cone shape that was carboned up. Soaking it in engine degreaser cleaned it up fairly well. Reinstalled the piece and started the unit and it works as it should. I suspect that removing this part from the muffler every month or two for cleaning will keep the problem from reoccuring. Wonder why the repair shop didn't tell me that this part could be removed from the muffler for cleaning?

That wire mesh is the spark arrestor. I would suspect that you might be a little oil heavy in your mix if it is clogging that frequently. However it may be that your prior cleanings were letting it exhaust enough that it ran fine for another half hour until it clogged again.

Oldsnapper28,
I have the same issue with the same unit and tried everything. So is the fix for this - removing this cone shaped wire mesh in the muffler or just cleaning it in engine degreaser?

does anyone know what this wire mesh does? I'm thinking it reduces sound when in operation?

My unit is 1.5 to 2 years old - it ran fine the first year and this started happening last summer. I believe the problem stems from sitting all winter without use to clean the engine and fuel lines out.

Thanks for your help! shipleych

I have a ryobi cs30 that will start for about 10 seconds then shuts off, i have cleaned carb, replaced hoses, primer button, cleaned muffler, and other stuff that seems to be pointless.
can anyone help i have been fighting this for a while now and dont have money to buy a new one?

I have the same unit and was wondering if anybody had any trouble with the cylinder head coming loose. The three Torx head screws that hold it keep coming loose and it flat won't run. The last time, I put some LocTite on the threads, but when I ran it for a few minutes, it quit. Any suggestions? Maybe some gasket material between the head and the cylinder?

it seems to be a vacuum leak. as i started it and before it would die i sprayed starting fluid around the carberatorand it would keep idling. the more i sprayed the longer it would run. it looks like the gasket between the carb and the black housing may be bad but you can't get to it.i removed the two nuts inside the air filter case but it looks like it is pressed on.im afraid that the filter houseing may crack. does anyone know another way to remove this and get to that gasket?

Two Cycle Engines Can Be Real Monsters Compared To Four Cycles. LOL Will Help! I have found almost all of the problems listed below on these trimmers.

1. Mainly blocked spark arrest screens due to too much oil in fuel mix (which some do not respect).

2. Sucking air due to bad fuel lines and primer bulbs would be 2nd common problem IMO.

3. Fuel filter, carb & fuel screen if fuel is fresh and treated with StaBil etc. every use is low IMO.

4. Lack of respect and understanding maintaining is very high IMO and causes me to pass on services.

A good example of a blocked spark arrest causing back pressure and poor or no engine performance.

1. IMO too much oil was used in the fuel and it was bad to let it get to this point.
2. It started easy, idle w/o power until the screen was cleaned, by heating red-hot (lighter etc).
3. Other Tell Tales = no visible good exhaust, feel or sound and not to mention the mess that is seen.
4. My friend had no idea mixes varied per age and Mfg printed ratio per item (probably 16:1 in all newer etc.

I'm not bold enough to go 50:1 with my (2) old late 70s saws and old Green Mach trimmer spec is 25:1. It would be ideal to use my boat's left over (summer's) 50:1 fuel. I add to it to meet Mfg's specs. Old Fashion! I'll Get Bold "in 10 years" and go 32:1 on the old saws and Green Mach (now 16:1 and 25:1). My bad experience was to have one 16:1 saw lock with 50:1. I feel the 100-degree heat played a part, which has me still using 16:1 in the old saws. Most of all, I have never seen a mess or excessive smoke like this on any of my equipment.