sound like you need a tach, in order to get full power the high and low speed needles need to be set right. sound like your low end isn't set right, on a 4 stroke if your not familiar with them you can not set the hsn by ear. All turns are started from full closed, if you need 4 turns you need to pull the carb and clean it and change the glow plug for good measure. Set the needle by leaning until it peaks in RPM then richen it. Also just setting a needle based on the book is just dumb, sorry if that sound harsh but it's true, the book is a starting point, not a needle setting guild. Set the needle based on what the engine is doing.
Start sloppy rich, if that means 4 turn then do it. Then lean for peak rpm and back it off 3-400 rpm.

If propped right you should get a 2100-2300 rpm idle and 9000-10000 on the high end and a faint but visible smoke trail in the air.


The low end has to be set right as well. And it requires starting and stopping the motor a good 10 times and 15 min.

incidentally did you break the motor in right according to the instructions. They are serious about not exceeding that 4K RPM when first run, and I don't exceed 6K until the 3rd tank and don't fly until the 4th-5th tank.

Also it is cowled? if it is is the cowl vented properly?

What plug are you using

what prop should be around 13x7 12x8 14x6

what fuel, I like ys20/20 but you need at least 15% nitro and 20% oil

Is the tank set up right. 2 line system, with the nipple on the same lvl as the carb barrel. no restrictions in the line, if you have a fueler valve try running without it, you might be getting an air bleed.

How old is the engine, how much run time, when is the last time the vavles were set, I need to do mine it seems every 6-7 gallons