Muhr , the effect you are describing is bound up in the fact that a KZ carb is way too small for a 50 Hp 125 engine.
The airflow velocity is VERY high , thus the venturi depression created necessitates a very small main jet to achieve the correct A/F ratio.
This also means the needle/tube combination has a very small annulus area at WOT.
In fact a well tuned KZ will rev to 12,000 with no main jet at all - been there done that , not intentionally I might add ( dumb or even dumber ).
But back to TeeZee dilemma , in this case the partially closed slide is decreasing the carbs airflow , way less than it is decreasing fuel flow from the emulsion tube nozzle , thus its (edit) :leaning the fuel curve over the top of the pipe.
This is evidence of the fact that airflow thru the venturi continues to increase past the power peak , but less fuel is required at this point , as the combination of scavenging and trapping efficiency % is decreasing even faster
If you had an electronic PJ this could be switched off , to achieve the required fuel curve past peak power - and this would increase the overev power exactly as per the red curve.
But in this case I would suggest fitting a much bigger main air corrector jet , this will need a comensurately bigger main to get the peak power fueling/egt the same , but then the big air corrector will
continue to lean off the overev fuel curve automatically.
I have done the reverse of this several times to stop having to run a huge main to prevent an engines egt from continuing to run away past peak Hp , thus killing the peak power number with an over rich condition.
The same can be done by using a flat line ignition curve past peak Hp , thus reducing the pipe egt/heat runaway, so reducing the need to add fuel to help cooling - not power.
Again - proving that your engine is doing just that , with a flat line ignition .
Always a dumb idea.
Edit - i mistakenly wrote leaning - richening is correct - sorry
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
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