my heli got a OS 50 SXH and the idle valve is factory set at the best performance position as it said in the manual. so l would expect no adjustment needed at the moment.

The needle that l talked about was the "mixture screw" since the idle valve is set.
l know different people would have different setting for their heli, but for the "mixture screw" would be very simular because if you got the same engine then you should have a very simular setting for the needle. l don't think an identical engine could operate with same eg. RPM or Max RPM in more than 1 turn while using identical fuel

anyone could say something about their engine setting and fuel used?

Thanks a lot