Small Engines (Lawn Mowers, etc.): echo gt200r weed eater bogs out at max throttle, air gap, adjustment screw

Question
QUESTION: I really need help with this one John.  Here's a list of what I have done so far.  I have replaced air filter, fuel filter and lines, cleaned spark arrestor and clean carb.  If there is a fuel adjustment screw on it, I can't find it.  I have looked everywhere.  I believe I have a problem with the coil.  How do I advance or retard the timing and what would be the proper air gap.  The coils only adjustment is for the air gap.  Is there a possibilty that the flywheel could be adjusted for proper max throttle running?

ANSWER: Before you go that far, remove the muffler and make sure you don't have any carbon deposits built up restricting the exhaust flow.

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QUESTION: There are no carbon deposits.

Answer
The timing on that unit should not be adjustable. The only adjustment is the coil gap. It should be .012.
If there are no exhaust restrictions, then i would say there is a carb issue. There should be fuel adjustments on that carb. But if there isn't, i would say to rebuild the carb, or replace it.