Saw is piston ported.
Compression test won't be affected by reed ( it's below the piston ring), but crankcase pressure whether positive or negative will be reed influenced affecting fuel delivery.
Engine has three main 'systems'.
Eliminate each one 'system' by eliminating possible problems within each 'system' for testing sake.
1. Fuel. By using starting fluid you have bypassed it. If spark is good, timing good, and compression ok...it should 'pop'.
2.Electrical. Two quick checks. Spark, and timing. You said spark is, "nice blue". That's good. Now timing. Two checks: First is Air gap should be 0 .010- 0.012 (I think). Air gap will affect timing.
Second is flywheel position. Either compare a picture of magnet position to a coil pick up leg, or pull the flywheel. There is a machined key way, and it used a steel key. It's possible by unlikely that the key, or crank cracked/sheared, but possible (unlikely) that the flywheel key way cracked. But eliminate it by checking. Ususally when a key shears it craps out right away.
3. Upper & Lower engine assemblies that develop BOTH Positive & Negative pressures by the crankcase, cylinder, and piston.
90-100 PSI is on the low side, but should 'pop' with starting fluid. Try the oil test to eliminate a stuck ring, and or damage wear. It's quick, easy and reliable.
It PSI increases...start there. If not... you most likely have a crankshaft seal that's bad. That saw uses needle bearings, which are a durable as ball bearsings. As time is put on the engine, and they wear normally, the crankshaft moves more radially, and that wears the seal lip.
Pull the clutch, and flywheel examine for wetness at the lip. Also try to move the crankshaft,..Up/down & left/right. In/out is normal.
If it moves....bearings/seals are worn. R & R.
