Guys, on my new Arrow RTF, the Evolution engine manual that comes with it instructs you to set the throttle trim to the mid position

to give you 1mm of throttle open at idle. The JR 400 Tx manual instructions just say you want a 1/16 inch opening at low throttle,

stick all the way back, no mentioning of trim setting. This is my first fuel engine.

I have the 1mm or 1/16 inch opening BUT ONLY WITH FULL UP TRIM SETTING.

Are there any problems I can run into with the throttle trim on full up or should I adjust to mid?

Thanks!

Left photo is at mid trim (no opening at all)......middle photo is at full up trim..........right photo is full throttle and full up trim.

I don't want to make that first post too big so I'll ask down here:

Is the "only" reason you need the engine to idle with throttle trim is so you can kill the engine by flipping the trim down
and shutting off the air ?

I've watched a few at my club have to put (and very carefully too) their finger over the opening to kill the engine.

Needless to say I don't want to have to do that

Generally you set the throttle trim to the high trim setting (towards the top of the case) and adjust the throw so that the engine travels the entire range. The low engine trim is used then to kill the engine at low idle. Unforturnately, the basic 4 channel radio does not give you the option to dial the throw in from the transmitter. So you have to do it the way we did 25 years ago, trial and error. You can adjust the total throw by where you connect to the servo and throttle arm, plus by rotating the arm on the servo you can cut the total throw. Get it close for now, and you can always use the throttle trim to lower it enough to land.

BTW, the Arrow is a very good flying airplane. Good choice!

Yes, the finger on the carb is a very bad idea. Better to just pull the fuel line. Also be sure that the servo does not stall against either end of travel. They should not be humming.

Thanks HighPlains,

I have servo hum at any trim setting less than half but at half there is zero opening on the barrel.

I just checked it out again, it appears that servo was never meant to be at low throttle with trim bottomed out,

that's what was binding it. At full up trim I have almost the 1/16 inch opening but at full throttle its not full open.

After I adjust the carb linkage out it should be fine. I may rotate that horn too.

Thanks!

hi i learned to fly last spring on a hanger 9 arrow with evolution .45 trainer i noticed that you still have stock three blade prop on it. if when flying it it seems to be pretty lasy on take off you might want to consider a 10x6 two blade. another thing i did was take off the stock flywheel and put aluminum flywheel on you can get from evoluition. i also was having problem with the way it was running and took the baffle out of the exhaust and it made it run alot better. just thought i would share my experiences with you might help might not. i liked having the power that these simple cheap mods provided. i think the other guys ansered you questions fine. you just want to make sure you can cut the trottle off without putting your finger over the carb and you don't whant to have the servos screaming at you because it will eventually burn up a servo.