First: Clean, Fresh No Ethanol Fuel? [EDIT]: Since You replaced the Carb, I gotta ask - same/correct one? Fixed Jets, or Owner adjustable? High Speed Jet may be plugged? Fuel lines all perfect, no cracks, correctly attached/run? Zero trash, sand, Water in Fuel tank? Fuel Cap vent works? (Loosen cap to check, but keep upright so no leak/fire during test)!!!
Sounds like it might be trying to seize.
Two causes are most common: failed (even one time) to mix oil and gas properly. I will assume that is not it.
Second cause: Heat! Have you checked and blown out all the grass, weeds, etc from the cooling fins, and the flywheel fan?
Tertiary cause that pretty rarely causes something similar- Exhaust is restricted by crud that has accumulated. Cause of this is too much oil in the mix - Two-Strokes need CORRECT FUEL/OIL MIX, and use Two-Stroke Oils! And too much light throttle! Two Strokes like to be WFO, doing work, not idling (or just off Idle). Do not use trash oil, crankcase drainings, wrong oils!!! Two Stroke oil is engineered carefully to: have low Ash, not reduce the octane so much, lubricate (natch), stay mixed more completely, and more! So, to fix this, ya gotta remove Spark arrestor, and burn out/dig out all the gunk.
Finally, worth a check every time you have problems: Two Strokes really like Clean, Sharp electrodes, correct Gap, correct heatrange Sparkplugs. Years ago, Family had and raced Three-Cylinder, Two-Stroke, SAABs. The joke was: "How can You tell a SAAB Racer? Ans: He's the One with Six Sparkplugs in His Pocket!". Check that Gap, even if Brand New, out of the Box! Especially with magneto ignition - not a lot of spare energy to make a Spark. Exact Gap!
