Hello,

I am relatively new to RC Flying, so naturally I have many questions. I recently purchased the Nexstar Trainer as my first plane. I have taken it out on two occasions to attempt my first flight and have run into an issue which I need help with. After priming the fuel lines, I attach the power source to the glow plug and the engine starts almost immediately. The problem I have, is that I let the engine idle for a few minutes to get it warmed up, I increase the throttle to not even 1/2 power and the engine seems to flood within seconds. Even with the carburetor set on the leanest setting, the engine still floods. Any ideas as to why I might be encountering this problem and any suggestions as to how to fix it?

Thanks!

When you say that you have it adjusted at the leanest setting, are you referring to the high-speed adjustment (the needle valve), or the low speed adjustment (the screw in the center of the throttle arm)?

Your symptoms indicate over-rich low speed mixture. Usually the low speed needle factory setting is initially too rich, but the engine improves somewhat with run time & it is generally usefull to get some run time on it before messing with low speed settings.

As soon as you get it started, smoothly advance the throttle with the glo-starter still attached -- this should help get it up to speed without drowning. When it is running at full throttle, remove the glo-starter & set the high-speed adjustment so that the engine is developing very close to max power. If the factory NV limiter settings are correct, you should be able to run the engine at full lean on the NV without fear of damage.

Just in case they aren't set properly, when adjusting the HS needle, keep leaning it until the engine peaks -- try to go past the peak & see if it starts to slow down. If it does, quickly back off the needle and approach the peak again from the rich side. When fully peaked without slowing, richen the mixture until the engine begins to slow slightly & leave it there.

After a few full throttle runs you can set the low speed needle.

Shut down the engine & adjust the low speed setting by turning the screw-head, inside the hole in the center of the throttle arm, clockwise 1/8 turn.

Restart & try it out. Keep adjusting the low-speed setting in 1/8 turn increments until the engine will hold a steady idle & then accelerate smoothly from a prolonged idle.

If you get the low speed needle too lean, the engine will die away at part throttle, or quit sharply (no sagging or sputtering) when you try to accelerate from idle, or even refuse to start, or just run a few seconds and die.

If you aren't getting anywhere, ask one of your instructors to help you.

Hello Britbrat,

Thanks for your response. When I mentioned I adjusted to the leanest setting, I was referring to the high speed needle adjustment. I will have a look at the low speed adjustment and see what I come up with. Thanks again!

I think your problem is you are letting it idle to long and then guning the throttle. The motor will load up with fuel if left at idle to long and then when you hit the throttle it will start to flame out the plug. The next time you start it before you pull the plug igniter advance the throttle to half power to wet the pluh hot and clear out the motor.

i agree with dolsen. engines will load up if idled too long my question is did you break the engine in before running it lean?

I have followed the breaking in procedures that OS supplied (unless I did it incorrectly?). I've only run the engine twice since new. Is there any other suggestions that anyone has on how to properly break in an engine?

Thanks!

the engine IS flooding, no way it should idle that long..in about 15 seconds when you cant hold the muffler the engine is warmed up enough... you are drowning the plug (loading up the engine)...Rog

Engines that are properly tuned can idle indefinately and then accelerate smoothly to full throttle from idle. It's not a case of idling too long, per se, -- it is a case of improper mixture adjustment, particularly low-speed mixture adjustment. Once that is fixed, it will idle until the tank is near empty & still accelerate smoothly to full throttle.

I'm not sure if it was a break in issue or something else? I tried what putting the throttle up to 1/2 just after starting the motor, it struggled a little and wanted to flood, but then I slowly brought the throttle up to 100% and it didn't stall, so it seems to be working well for the time being. I haven't had a chance to get it out since then (great Canadian winter - YAY!), so it's hard for me to say if it's been resolved. But for the time being, thanks to everyone for their thoughts and suggestions!

Quite often an engine will struggle the first time after start as you come up to speed. This CAN be normal. The test is to get it up to full speed, return to idle, remove the plug battery and see if you can accelerate the engine smoothly to max. You should be able to just go from idle to max without hesitation or sputtering. If it quits or sputters you will need to lean the idle mixture carefully in 1/8 turn increments until you are satisfied. OS usually ships these engines too rich. Better that than too lean and burn them up is their motto. Be very careful adjusting the idle mixture, I recommend stopping the engine to do this. Sharp prop. [:@]
If flying with a club or experienced fliers, they should be able to help with this.

your NEXTAR should have a already broken in engine from the factory, although the settings should be rich when you open the box if you let it idle to long like the posts have said it will load up. before take off straddle the fuse and run it up to full throttle to clean out the load up after a couple of flts. 3 to 5 tanks full, have a engine guy from your club lean out your motor a bit for max performance having a experienced club member help out saves you allot of time. after you see it for yourself it makes it a whole lot easier to do yourself knowing the right sound to listen to. like bruce88123 stated yours might be the one rich one but the basic break in should have been done before assembly.the rich settings are so you dont burn your new engine up in the beginning. you live in Ontario are you flying in cold conditions? if your fuel gets to cold it will thicken which can appear like you are running to rich also in northern cal its cold but not like Canada I store mine in the laundry room out of the way but warmer than a cement garage floor or shop. your engine warms up in about 30 seconds of running at full speed. good luck.