If you have the 19mm PHBG carb it is supposed to bog a tad at full throttle . That is your safety zone at red line as that carb lets a lot of flow through it! The Air/Fuel mix has to be properly charmed.. . ''very important'' So you do not burn your motor up. The generic term I have heard it by is tuning for altitude. You are going to reach your top RPM' s and have all the power you need when tuned this way.
This is how the PHBG tuning tutorials I read ALL said to do it....
When I am just getting into a hill or aggressive hole shotting from a stop the added richness helps me with needed extra power nicely . When getting to full RPM I simply back the throttle off just a tad and the motor just does that so00 beautiful song and hum!
At this stage of established acceleration if I do not slightly back off from full throttle the bike mine will stumble. These are racing motors and the tutorial on the PHBG carb from moped army even says to tune this carb this way!
http://www.mopedarmy.com/wiki/How_To_Tune_PHBG_Carburetors
I have tuned it by way of main jet before to see if I could more speed. It is not worth it and you do not magically get more speed with this PHBG model carb..
You are at sea level so really doubt you need to reject your carb? All carbs come generically jetted for sea level.. I also don't know what all these carbs are coming with jet wise stoke, and have never run at sea level?
Think 90 main jet Mebbe at second needle notch? 50 pilot a W9 needle with a 262 AU atomizer and a 60 choke jet for stock sea level... ??? No body ever say's what they are using on a 19mm PHBG??
This full throttle deal only happens for me after full acceleration and the motor is not seeing that load of acceleration. Humming along a full speed. Liken to 4 stroking..
There is a static idle adjustment and then a fuel adjustment screw on your carb. The fuel adjustment screw represents the first half roughly.. 1/3 of the lower throttle dynamic. Put a hotter plug in it to. I run a NGK B8EGV Stock is a 10 on the S6S engine..
Have had the recent opportunity to to work on a lot of 2 stroke trimmers and chainsaws lately. Tuning them for altitude is the same way I have been taught . On those particular carbs they had a high side and a low side adjustment. I set the high side to where the motor sings it's best at wot then go a turn back and set it richer. ''Safety Zone!''