Derek Gray 1

I have a HobbyKing YAK 54 40e1380mm wing span and I have lost the build instructions. Can anyone help with C of G position and recommended control throws

I have a SC52fs, it runs fine, even tickover. The issue is the last half of the throttle does not produce much in the way of a power/rpm increase. At half throttle it's pulling 9400rpm at full throttle it pulls 10000 rpm but sounds a bit uneven in the air at full throttle. I am using contest 10 fuel, os f plug and a 12x5 MA prop. The needle settings are High end 1 and a half turns out, and low end (idle) 1 and three quarter turns out. The engine is quite new, only had half a gallon through it but it picks up well from a 3500rpm tick over even if the throttle is opened quickly and smokes as expected. I have tried a richer needle setting (rpm 9300 on ground) but the model is under powered and staggers around in the air. I have opened up the idle setting making it richer but it causes the engine to cut in the air after a few mins flying. I have been told a 12x6 or 7 prop will help as it will load up the engine? At the moment the aircraft flies well at half throttle with full throttle only slightly effecting vertical climb performance. I cannot lean out the needle as it may damage the engine and spoil the good throttle response at the bottom end. I have the tank center inline with the needle valve and have even tried a smaller 6oz tank and plumbing. Any suggestions guys @import url(http://www.modelflying.co.uk/CuteEditor_Files/Style/SyntaxHighlighter.css);@import url(/CuteEditor_Files/public_forums.css);