I have the MightyLite 26bv....will only run at half choke. When turn knob to run, it dies. Does not reach full power ever.

Sounds like a lean condition. Rebuild carb, replace fuel lines and fuel filter and you should be ready to blow the leaves.

Sounds like the carburetor needs a cleaning and rebuild. Make sure that you replace the diaphrams also while there.

I hope this is helpful for you.

sounds like a carb problem You will have to take the carb off and strip it down to parts clean out all the ports with a good cleaner I use brake clean reassemble and reset the High speed and low speed jets at 1.5 turns out then adjust from there

You probably need a slight carburetor adjustment. Try to turn the L mixture screw (the one near the bottom of the carburetor on the air filter side, closest to the engine) 1/8 to 1/4 of a turn counterclockwise. These mixture adjustment screws ( L and H) have odd heads on them and conventional tools won't turn them. I use an automotive type plastic wire connector (around 22 gauge) with a ring terminal end which I can hold. Tap the plastic end of the wire terminal connector onto the head of the screw with a small hammer and this will enable you to adjust the L screw. This adjustment will increase you high speed side and possibly allow it to run off choke in a regular manner.

Zama Carburetor:
http://www.zamacarb.com/tipspage.html
Walbro Carburetor:
http://tech.flygsw.org/walbro_tuneup.htm

Two stroke gas equipment needs a good long warm up. The heat is part of the deal. Set the choke on full chioke. Prime the bulb till you see the bulb is full. Turn the kill switch if you have one to "on" and fire it up. let it run at idle as long as it will or for a minute on this choke setting. If it dies restart and let warm up. When it is running ok but a little bit boggy then move the choke to open or half and give it some gas. If it responds then go to full open and crank it up a few revs. If it bogs or dies your unit will need service. The diaphragms in the carb are replaces as a kit and run about $6- 10. They are also easy to do if you can read and hold a screw driver. These go bad from fuel hardening every 14 months or so along with the primer bulb and hoses. Get all of this online from parts stores. Whole repair makes it like new forabout $15.00 or let someone do it for you for about $ 50.00.

After you start it and are in the second stage of the choke (half choke ) let it run for awhile until it warms a bit then try openning choke and going to full throttle.

make sure your fuel mixture is correct also check t your air cleaner it will not run right without it or if it extremly dirty

Agreed all these cheap trimmers are built at a price the only way to tune them is to take it to the dealer, The special tool costs nearly as much as the machine.
So most machines under 100 dollars are throw away and replace its bs but everything is ending up the same.

have you tried changing the air filter and spark plug?