OS Engines .32 Heli
What fuel are you using? Include oil percentage and nitro content as well...
You should be using a heli fuel with the appropriate oil percentage. I would suggest for an OS Engine that you use 20% nitro with at least 18% oil content.
Your description and ascertain sounds a little strange to me...
If the engine is running lean, there is a lack of fuel not an over abundance. "Lean" generally describes a condition in that the engine is hungry for fuel. The fuel mixture lubricates, cools the engine and provides fuel for combustion.
Leans runs are caused by over-loading, lack of cooling, intake tract air leaks, either bad or the wrong fuel and or incorrect needle settings.
Adjust your hi-speed main needle to 2-turns out from a light seating CCW, the low/mid transition adjustment should be initially set at 2-turns out from a light seating CCW as well.
Helicopters represent a challenge when trying to needle due to the blades wanting to engage when you throttle up. Therefore you are afforded a challenge... I suggest that you get some help from an experienced helo pilot that can offer some insight on how he accomplishes the tuning. I personally set the needles as previously described. Hold the rotor-head, start the engine, maintain a slightly fast idle without engaging the clutch and warm up the engine then idle down until the engine wants to die, bring up the throttle until it will maintain an idle, note if the engine sounds rich or lean. Keep in mind that you would never move the low/mid-range needle more than a 1/16" of an inch at a time and wait for the results. From here use the pinch method at idle, pinch the fuel line momentarily, if the engines picks up rpm instantaneously it is lean, if it is lazy and runs on for more than say 10 seconds or so it is rich. Adjust the low/mid-range needle accordingly, CW to lean and CCW to richen. Once you accomplish this initial setting you are ready to make a stab at the hi-speed setting. This is were it gets tricky and dangerous. You can weight down the machine, clamp it down or whatever, you can also program the radio for a condition that will allow negative pitch to push the helo down rather than create lift. Once you have decided how you are going to hold down the machine warm it up and transition to full throttle, take your time and make numerous adjustment's with the hi-speed needle until you feel the engine is running at peak efficiency, look for a smoke trail as well. It will take several attempts to realize the correct setting, sneak up on it and do not lean out the engine too far. Rich is safest, however to rich is of no benefit...
NOTE: you should always stand back and run up the throttle never try and adjust the needles while the blades are spinning.
Now finalize the adjustment of the low/mid-range needle. Throttle up note if the engine bogs down or stumbles/blubber's into a mid throttle range, bogging down is an indication of lean setting, while stumbling is an indication of being to rich, adjust accordingly. Remember only move the needle in very small increments and test again... Once you are able to transition, see if the engine will idle, if not adjust your ATV or idle stop to find the sweet spot. Again do the pinch test to see where you are at.
The hi-speed needle only effects the wide open throttle setting while the low/mid-range needle effects idle and transition off idle and upto midrange rpm.
Helicopters ideally operate at two rpms idle and full throttle.. The pitch is adjusted to accommodate changes in lift for various flight conditions...
Good Luck and be careful.