Keep in mind also, that on a piston-port two-stroke engine, it must have decent crankcase compression, as well as cylinder compression, to operate correctly.
Leaky crankshaft seals are a prime cause of loss of crankcase compression.
They are easily checked; by positioning the seal uppermost, giving it a squirt of fuel or light oil, and turning the engine over.
Bubbles, or the fluid getting sucked into the engine, = knackered seal.
