Dear Pe,

We have been fighting against the carburetor of this engine in order to set the needles properly, during two months with three different MVVS 116 engines, in a work bench and in the plane, on the ground and in the air.
Let me to explain our experience.

Starting with the factory settings H 1 turn and 5 minutes (maximum rpm less 200), L 45 minutes, we put the engine up-side down, in a work bench or in the plane, and the engine run rich because when WOT the engines needed some time to burn the gas and didn't reach the rpm as when the engine is right-side up. We closed the L needle 5 to 5 minutes till we had a good response, it meant a total amount approximated of 20 minutes, but when we put the engine right-side up the engine quit when quickly WOT. At that moment, we managed opening or closing the H needle but without success. The solution was to opened the L needle slightly in order to have a crispy response without quitting but when we put the engine inverted again we found same problem, lack of response; it happened when flying in knife edge motion as well. This happens on the ground and flying. After two months trying to investigate the different solutions we have throw the towel; we do not find the needles commitment , up-side down versus right-side up.
We have checked the tank, we have changed the factory hose by 4 mm Tygon, we have put a balsa box, we have used a velocity stake, we have opened the hole of the filter to 3,5 mm, we have used a felt filter, we have put baffles in the cowl and nothing clearly worked.

Is it absolutely necessary to use the hose than comes with the engine from the factory?
Does the felt filter in the tank do some effect?
Does the balsa box work in this situation?
Is it possible to substitute the carburetor for another less critical (it is understood that this carburetor was designed for carts used always right-side up)?
Is it necessary to guarantee always a minimum of 4 mm of line tube from the tank (filter, inside tubing and connections)?

Sorry for such amount of questions but please understand that we are desperate because of so much time trying to get the proper settings.
Thanks in advance and best regards,
Andrés Guillamot,