90 Marathon 2 Stroke no power in bottom end

[seahunter]

This thing is starting to drive me crazy. I've tried just about everything I can think off. I must be missing something obvious.

Symptoms:
Slow, no power on the bottom of the rpm range. Once it gains RPM it runs pretty well until the RPM drops back in the lower ranges again.

You will be running along and out of the blue you will get a couple of dead misses then it will run OK again.

Existing Conditions:
Compression 95 PSI. Adding oil to the cylinder does not increase the compression.

It starts on the turn of the key, even in very cold conditions

New seals installed last Spring

Almost acts like the timing is retarded. Checked, in the middle of the adjustment slot

Has HEI ignition upgrade on it.

New carb and the plug’s insulator is a nice light brown color.

Motor sounds good while running. No pre-ignition, bangs or rattle

Pulsar fails ohm tests. Still outputs ½ volt when cranked

A new spark plug seems to help the miss for a while. No real affect on the no power in the lower RPM issue

Removing muffler has no affect