I recently put my Rap 50V in the air and it flies well, after breaking the TT50 in. I've noticed that regardless of how I set the carb mix, the engine runs rather rough, like it's cutting in and out. It's hard to describe. I wish you could hear what I'm talking about. When it cuts out, the tail twitches at the same time. I've had five heli's before, and have never experienced this problem, regarless of mixture settings. The problem seemed to vanish, for a couple of tanks yesterday, but then reappeared, later. By all other indications, it seems that the engine is properly tuned. It flies with plenty of power, it passes the pinch test, and plenty of smoke, to boot. A friend of mine, the local heli xpert, said that bad main shaft bearings could cause this. He said that at certain RPMs, the shaft could hit the "flat spot" of the bearing, and cause a slight drop in RPMs, thus causing the tail twitch. Although the heli is new, he recommended changing the main bearings, to play it safe. Has anyone had problem before?
Mike

ive got an os 50 doin exactly the same thing. runs great heaps of smoke ,cool , just has this habit of cutting in and out ad therefore making tha tail tiwtch mine is especially bad when i powerclimb.. i thought it could be a lean spot. maybe some crap in the carb or fuel filter ,, ive ripped out the gine tightened all trhe bolts cleaned the crab the fuel filters so heres hoping ,thogh i have my doubts . im gonna fire it up this afternoon so fingers crossed .

be sure u dont have any leaks in your fuel system also. that has caused a friend of mine's freya to do the same thing.

I found two older post, over at RR, that describe the same problem that I'm having. The term,they used,was 4 cycling, meaning the engine is changing, back & forth from 2 to 4 cycle, thus causing the tail twitch.With my TT50, you can clearly hear the tone changing back and forth. The cause given, for the problem was improper engine tuning. One guy said he fixed the problem by slowly leaning out his high speed needle, until
the 4 cycling stopped. I'm thinking that I'm running my high speed richer than most, according to other post I've read, so I'm going to try slowly leaning out my high speed, and see what happens.
Mike