Carbs either need to be cleaned or replaced.

I have SRM2200 which uses same carbs, but don't know your vintage. Mine has a Zama with limiter caps over the mixture screws.

1) If you remove (pull off) the limiter caps you might help, but not likely. The outboard screw (nearer the air cleaner) is main jet. Suggest you try a 5% to 10% mixture of Seafoam in the fuel. If you can keep running, the Seafoam will gradually dissolve the gum. Cheap solution, but probably only 10% probability of a fix.

2) Next is disassemble carb and remove all rubber and elastomer parts, then soak in a good carb cleaner, rinse, blow out and reassemble. Initial mixture settings are 1 1/2 turns out for both. Better solution, but still not bullet proof, because there are some passages and screens behind welch plugs. To do it right, you need to remove (with a chisel) and replace (with new and sealant) each of those welch plugs and clean underneath. More trouble, and I give it 50% probability of success.

3) Replace the carb. Easy, but expensive. Again, remove limiter and set mixture screws to 1 1/2 turn initial. adjust from there after warm up.

I don't see any mixture adjustment screws in the parts breakdown of this rotary-type carb. The older ones at least had a MAIN mixture screw concealed under a black plastic plug and blocked by a brass insert. Try installing a Gasket and Diaphragm kit. I would NOT recommend using high PSI compressed air on it as these carbs have sensitive check valves that are easily damaged. I also recommend NOT using any strong solvents or carb cleaner sprays on the carb. The harsh chemicals swell the check valves rendering them inoperable. There are probably rebuild kits available if needed and include all the G & D parts.
If you want to try, you could get an older rotary carb like an RB-K70 or K75 which HAS a main mixture screw. Adjusting it eliminates the "lean" running problem.

I was mistaken. I looked at the wrong carb for the SRM 260. For that, I apologize. I did see that it has a slotted Main mixture screw. But, I fail to see a Low speed mixture screw.

Looking, i find no plug on either side where a fuel mix screw would be on other carbs. I guess ill try taking it apart and soaking it even though i use it frequently - not like i let it sit for months on end.

BTW, the carbs are the "rotary" type that turns on a vertical axis.

Did you fix the carb? If there is no main mixture screw to access, then the best alternative is to install the gasket and diaphragm. It may or may not help because due to newer EPA carb regs, the manufacturer has to set these really lean at the factory.

My friend just told me that the echo has carb problems on these new non commercial trimmers. He fixes a lot of machinery and tools. Stated that these are throw away carburetors? Can you recommend a trimmer please?