Almost like hitting the Rev Limiter?!!?

[gary55]

isn't that what 4 stroking is? your run it out and on top it gets deeper sound and choppy running like every other fire is drowned bcs jetted too rich

yes. The reason is that the mixture is to rich in fuel and starved for oxygen so it requires another stroke before their is enough oxygen to allow ignition.

 

[gary55]

Spark plug looks normal, running a 40:1 ratio, havent completed break in period yet. I think I should wait till I run a tank or two before anything

Not a bad idea to break in before adjusting through re-jetting. I generally advise toward the safe side and suggest 6 oz. per gallon for 1st. gallon then drop to 4 oz. after that. I'm pretty sure you will need to go to a smaller jet when the time comes. Probably 68 or 66. start with the 68 first.