Best post I've ever read on the ST carb issue Xjet. My experiences concur entirely. Particularly well constructed explanation. Analytically accurate, emotively honest without brand or commercial prejudice.

But to mention for the sake of clarification.

It's not even case of overpowering. Fitting the correct power range engine to a particular model such as a the average trainer where the effect of an excessivly high idle is exacerbated by very small changes (increases) in either angle of attack and speed in particular (V²) due to its wing efficiency leading to an inescapable characteristic that it will float or hold-off 'forever' chewing up the LDA if there is too much lift being produced due that combination of thrust (speed) produced by that high idle. ie: "Throttle controls rate of descent".

The trade-off, which you correctly identify, is to compromise by lowering the idle resulting in an unstable gurgling transition, with hesitatory and distracting engine acceleration during execution of the touch and go, go around or missed approach semi assuring a dead cut and EFFATO if the stud opens the throttle rapidly without understanding. That MAG carb design characteristic is exacerbated on smaller ST engine sizes (eg: 40) by the relative size of the carb throat, which is simply huge in comparison to brand peers. eg: nearly 10mm on my S40K ABC MAG in comparison with around 7mm on most Japanese .46s. Sure this makes for a stinkin' hot high end at full honk when that boost port is in full song, but also for excessively fiddly overly complex carb tuning and rubbish transitioning without an excessively high idle in a world where a majority of most McFlyers can't even hand start and haven't a clue whether an engine is lean or rich when it won't, nor have any have no idea how to diagnose or adjust the low end mixture needle.

I think it most tragic where excuses are proffered, typically "unrealistic to expect any engine (in the particular capacity range) to reliably ide below 2800rpm". No argument that certainly holds true for ST's 40 IME, but certainly not for ENYA's, O.S.'s TT's et al. In fact, for training, it's vital that one achieve a stable sustained low idle, with an equally reliable steady transition to full power, touch and go after touch and go after full stop, or after prolonged idle whilst appraising the student of particular points to take-off rinse and repeat.

Neither TT or O.S. nor ENYA's TN carbs present with these issues so typical of the MAG, and they also have a much small effective throat diameter apparently without detriment to high end performance. And of course, with the air bleed examples of ENYA and O.S.' LA training engines with their typically small throats ensuring good suction, their super reliable low idles and rock solid transition is the model of what is achievable. Why is it that one can achieve a stable idle and transition from as low as 1600rpm with any and all of these engine's carbs, yet anything below 2800rpm on the same capacity ST fitted with a MAG results in the 'gurgle 'n gamble'?!!! Two words. Carb design.

I for one am not only gobsmacked at the blind prejudice, but at simply beyond tired of hearing the perennial Secret Club of Superior Technique Tuners utter nonsense about MAG carbs. Blowing in tubes whilst consecutively reciting three "Hail Mary's", tweaking spraybars, "3000rpm idles = normal and OK".

Such a shame ST persist with fitting this indisputedly flawed design to their engines - which are otherwise absolute bull performers!