I was given 3 Sthil weedwackers, all would kinda start but NO RPM.sigh, 2 stroke jokes.....

the CURE was to remove the 'spark arrester' from the muffler, CLEAN the buildup of soot/fuel off it, reinstall, vrooooooooooooooooooooooooooom !!!

I gave one away, as I really don't need THREE.

Doesn't matter WHAT one uses, if it isn't maintained carefully, it will be a failure.

Battery powered tools that don't get regular use, wind up with batteries that self-discharge, then won't charge, so as noted above, pick one that uses the same batteries as your cordless drill, impact, and stuff.  DON'T park a battery in the charger and leave it for months... even a fancy and expensive tool system (like my Metabos) will wind up with ruined batteries because they need to be EXERCISED in order to stay electrically 'pliable'.

Tiny 2 and 4 strokers share the circumstance of tiny carbeurators, and they're usually made of a die-cast zinc that does not withstand ethanol, water, and fancy 'additives'.   Running one without being particular about the fuel and oil will result in a very short service interval for your machine, and as the engine gets smaller, the orficies within the carbeurator will be more susceptible to clogging with debris from fuel, or even parts of the fuel filter, lines, tank, seals, and corrosion within the carb  itself, and with that, more frustration.

As also previously noted, the exhaust flame arrestor screen (in the muffler) will get fouled with carbon soot, and as it does, it slowly chokes off the engine, making it run really bad.

To combat these situations, use good fuel.  The premix'd stuff on the store shelf, albeit advertised heavily as 'good', is NOT my suggested first choice, and if I HAD to use it (at the equivalent of $18/gallon), I'd at least SHAKE IT UP good... but my impression of the stuff I used, is that it's a really nice can, full of overpriced nothing. 

Yeah, I could see a guy using White Gas (Coleman fuel) mixed with proper 2-stroke oil.  I've also seen guys who visit the local race track or airfield for their fuel, but I generally avoid using those simply due to possible presence of Tetraethyl Lead (TEL)... these little engines really aren't designed with the presence of TEL...  instead, I'll go visit the store chain that sells lots of 'no ethanol RV gasoline'... and I START by running a couple gallons into my car or truck, THEN direct it to the 1-gallon can (with oil already in it).

This way, if there's any debris, contaminants, or remnant of some OTHER fuel type, it gets run out'a the hose FIRST...

Pick good oil... don't use generic, and get your mix right.  Most of my stuff is Stihl... I do have a few others... 2 Echo blowers, and 2 Echo saws, one Shindaiwa 575... and some outboards.   The saws and blowers are all at the same ratio... the outboards are either 40:1 or 50:1, but need an Outboard Oil, as it's got a different operating criteria for the liquid-cooled circumstance.

The next two things are really important:

Don't baby the small engine... scream it.  When they're not working, they're fouling... if you don't run it hard, the combustion will be too cool, thus, incomplete, and plug that #@$ flame screen.

Next... when you're done, DUMP IT OUT...  put it in the Zero Turn, or something else that's much bigger, or use it for some other (safe) purpose, but get it out of the tool.  If the fuel is more than a week old, consider it expired.  Yeah, it might run fine, but keep the fuel fresh, and those seals and gaskets will last longer.

Expect that every two seasons or so, you'll pull of the shrouding, pull the muffler, burn out the oil soot from the muffler, pull down the carb, clean it with spray, drop in a new needle and gaskets, pull through new fuel and vent lines, a new pickup filter, new primer bulb, new air filter and spark plug.  Clean all the crud out of the shrouding, scrub any corrosion off the recoil starter, check the magneto gap.  On chainsaws, clean or replace the oil pickup screen, oil line if needed, and oiler pump... blow out all the residue, clean the groove, file the burr off the bar (and flip it), and put on a new chain, and sharpen and reset the depth gauges on the old one.

Do this process on all your little tools, and they'll do fine.  If you REALLY want good performance, look up each tool and look for the performance modifications that people have done to make them breathe better.  Typically, the emmissions requirement of 'noise' means the muffler has excessive baffling, retarded ignition, and a lean mixture setting...  correcting these things may make it a little louder, but you'll only need a fraction of the time to do the job.

On your weed trimmer, take that head off and find all the string, fishing line, and fine weed stems that've wrapped around the shaft right by the gearbox or shaft outlet, take 'em out... look closely at the seal (make sure it isn't damaged).

Now, the OTHER option is to put a generator on a small trailer behind your mower, and have a long cord on a reel, and your 120v trimmer and chainsaw there.  I have a Miller welder-generator on a trailer specifically for pulling to places where people need on-site welding assistance, and it pulls nicely behind my zero-turn.  If I need to do tree trimming, I back the trailer under my mobile platform, and use the hoist on the platform to lift up the weld-gen trailer and suspend it beneath, then I run an extension cord up to the platform deck for my electric pole saw.  I just drive the platform through the trees, and use the pole saw to knock off all the low limbs... so no need to have gas chain saws up there, unless it's a really big limb.

Last year I  purchased the EGO brand of tools for my weedeater (which has a power reload function for new string.... love it...) and my leaf blower.   This spring I will buy the hedge trimmer as well. 

Batteries are all interchangeable, so I'm never short of power for my needs.

I have been very pleased with these so far.  I didn't move to battery/electric to be "green" but soley because of less maintenance and can just pick up and go (assuming I kept the batteries charged).   

Oh Halll noh... if I"m gonna play, I'm gonna be comfortable when I do it...

Saturday In the Park... (Chicago)  on July 4th 2022:

When it comes to that kind of trimming, Adam, skip the string.  I use a Stihl FS-80 with a metal grass-mowing blade.  If you have lots of saplings over an inch, use the type with finer teeth... if it's just grass, use the 3-blade mower, it will clean itself out faster.

IF you're gonna be getting into the fence alot, you can use a cutting head with swinging type blades, they're available in plastic and metal types.  I use both, and I wear them out rather fast... but regardless of how you go about it, if you've got lots of area to cover, and lots of material to cut, you'll probably find that liquid fuel power is much more effective in that context.

I usually need a recharge LONG before these new batteries do!

I asked my local Stihl (and AGCO) dealer about the battery-operated trimmers. His response was that it depends on what you are doing. 

He says if you are using it (even chainsaws) for hours every week, stick with gas. But if you are like the average homeowner (which is me), he recommends battery operated. 

He said this wouldn't have been his recommendation a few years ago, but the battery powered equipment has come a long way.