Hi Guys,

After flying my Nexstar for 3 times now with an instructor, I still don't how to adjust my engine the right way. My instructore has adjusted my engine,but I wonder if he has adjusted it to be too lean. At first all my instructor did was adjust the high speed adjustment. On the second session the engine wouldn't start so he adjusted the low-speed. Now at first I saw fuel slighly coming from the exhaust, but now you don't see anything. The color of the oil on the plane is a little darker than the fuel's color. I read somewhere here that the color of the fuel. Could someone tell me if my engine is fine and this is how it is supposed to be or is there something wrong. I want my engine to live a nice life and not die soon.LOL

Thanks a lot.

Well I can't speak to what your instructor has done with it, but the instructions on my NexStar told me about the plastic stop on the needle valve that they have pre-installed from the factory that will allow us some adjustment travel but keep us in a range that will not be too rich, or too lean. I ran mine for a few minutes to warm it up then slowly leaned it a little at a time until I got a nice smooth idle, & good transition. It ended up just about at the leanest position possible with the stop on it. Since I aint no engine tuning Guru I thought it sounded like a good safety feature to me so I left it on & it worked fine for me. Did you or your instructor remove the tuning stop?

My instructor removed it as soon as he saw it, as he is a seasoned Nexstar flyer. The problem my instructor adjusted both the high speed needle adjustement and the low speed adjustment on the side of the carburetor.

Thanks

Well, I'll leave it to someone with more engine tuning knowledge than I have to help you then. Good luck

Greetings Ferocious Frankie :-)

Turn your high speed needle all the way in (GENTLY) (turn to the right) then turn the needle out 2 full turns (turn to the left).
Check your radio and carb before cranking, ensure that the carb is only slightly open and low idle setting on your radio.
Make sure that you can close the carb with your radio all the way.
Have someone hold the airplane and you start your engine.
Allow the engine to warm up before adjusting anything.
If it cranks rev up the engine and see if it will take full throttle without cutting out.
If it will not crank, turn your high speed needle (turn right) just a few clicks until it will crank.
Once you have a reliable engine run at full throttle pinch your fuel line just for a few seconds and listen to your engine.
If it speeds up turn in (right) just a few clicks.
If it cuts out, turn (left) just a few clicks.
Tune your engine until there is no change when you pinch the fuel line.
Then turn your needle (left) just a few clicks to leave it a little rich.
Once you have the high speed set and there is a good transition from idle to full throttle, no hesitation, have someone take the airplane and turn the nose up slightly.
Put you plane in the same attitude as takeoff and listen to the engine, if there is no hesitation then you are ready to take her up.
You need to make sure the engine is ready before takeoff.
LOW END NEEDLE Setting is set from the factory and should not be adjusted unless someone moves it before the engine is broken in.
Once the high speed is set and if you need to check the low end, allow the engine to warm up and with the engine at idle, pinch your fuel line and listen, if the engine cuts out the low end is lean, if the engine speeds up then your too rich.
When you make engine low end needle adjustments you need to BARELY move the needle LESS THAN YOU DID ON THE HIGH end needle setting.
Facing the needle RIGHT is lean, Left is rich.
If you adjust your low end then you need to go back and recheck your high side ((AGAIN.))

And that answer right there is why I left it to someone with more experience! wtb, I'm gonna save that. Thanks.

Thanks a lot WTB3886. I will surely post this to my favorites and refer to it. First I adjust the high speed needle. Then after I adjust that then I adjust the setting on the side of the carburetor. Am I right?

Yes. Then doublecheck the high. Once you get the low set, you will seldom need to touch it again unless the engine goes to a much different climate/altitude. OS seems to set the idles slightly rich to protect the engines from damage that can be caused by a lean run.

WTB,

When you say are pinch the fuel line, are you talking about the fuel line that goes to the exhaust or the fuel line coming out from the high speed needle? Also when you say after you set the high speed then you can set the low speed how will I pich thwe fuel line and listen when I have already adjusted it with the high speed. If I tune the engine first with high speed and the rpm doesn't increase or decrease anymore how will then I change the low end when I pich the fuel and the RPM doesn't change.

Thanks a lot. I just don't want to do something and then kill my engine and can't work it anymore.

You pinch the line just before where it goes into the carb.

The pinch test works at all throttle settings (to tell if rich or lean) but you are primarily interested in setting the needles at high and idle as very few carbs have intermediate settings available.

If you pinch the fuel at the low end and see no change you mixture is probably very close. then just make sure you have good acceleration.

You aren't going to "kill" your engine. Remember you can always undo whatever you have done or go back to factory "start" positions and begin all over again

When you say the low end, are you talking about the opposite side of the fuel line where it goes into the carb or is it another fuel line.

"Remember you can always undo whatever you have done or go back to factory "start" positions and begin all over again"

This is basically what I want to do.Take it back to the factory settings and start all over.

Thanks a lot.

Low end = idle RPM. Sorry for the confusion.

Instead of going all the way back to factory settings, just reverse the last couple of changes you made if you can recall them. Probably need to make the idle more rich at this point.

Actually -best advice would be to get with an experienced engine tuner at the field if you can.

When you set the "high speed" needle valve, you're setting the "big" needle valve that is obviously "the needle valve." And you set it with the carb wide open. You normally will start your engine with the throttle set about 1/4 open or wherever you're comfortable and it starts easiest. But to set the high speed, you do need to open the throttle fully so the engine is running wide open when you adjusting the needle valve.

When you have that set, you then are going to take the throttle to idle position to set the low speed needle. So when you do the pinch test, you're actually doing a different test than when the engine is screaming at full revs.

BTW, setting the idle is an entirely different deal than setting the primary needle. A couple of things are different.
One of the first things to do is to let the model sit for a minute with the engine running at idle. Then do the pinch test. But before you tweak the low-speed needle, do a second test. Let it run at idle for a minute and then jam the throttle wide open quickly. What you're looking for is the engine to simply jump from idle to flatout without stumbling or choking. This is actually the point of the whole deal about setting the idle mixture. The pinch test is a good one for either the full throttle test or the idle test, but you can fine tune the idle setting and the low speed needle setting by letting the engine idle for a minute or two and then slamming the throttle open. BTW, when you're testing the idle setting, you don't need to hold the model up, pointing at the sky like you do when testing your full throttle needle setting.

And another minor detail when setting the lowspeed needle. Shut the motor down to do it. It's lots safer that way. BTW.... setting your transmitter to run the engine at a slow idle and also be able to also shut the motor off is another thing you need to do........ chuckle..... yet another intricate detail, right?

I think the confusing thing about the pinch test for you was the minor detail that you do it with the engine flatout for setting the primary needle setting and with the engine at idle for setting the lowspeed needle, right?

Here's my engine tuning procedure:

1. Start the engine, leave the glow starter connected, and run the engine to max throttle for a few seconds. This clears out the exhaust, heats the engine up, and ensures your glow plug is up to temperature.

2. Return to reliable idle speed with the throttle and remove the glow igniter.

3. Using a tachometer, go to full throttle. Now start leaning out the High speed needle (thats the big one). RPMs should rise to a peak then begin to fall off. Find the peak, and then back the needle out again a few clicks such that you are running at 200-300 rpm below your peak speed TO THE RICH SIDE.

4. Return to reliable idle speed. If you were very rich before, you'll find your reliable idle speed may have dropped slightly. This is good.

5. Wait 20-30 second, then punch the throttle to full. If the engine goes to full speed without hesitation, you're done. Go fly.

6. If the engine hesitates, and then goes to full throttle, you're probably a little too RICH on the low end. Stop the engine, LEAN out the low end by 1/8 turn.

7. Restart the engine and return to step 1. YOU MUST RESET THE HIGH SPEED NEEDLE every time you adjust the low speed needle.

8. Repeat this process until the engine idles reliably, and doesn't hesitate going to full throttle.

The low end must be adjusted slowly. It is extremely sensitive, and its very easy to go right past the sweet spot.

Unless the engine has had a few tanks of fuel run through it, don't even bother with the low end needle. Wait until the engine is broken in. Once you get the low end dialed in, you'll never need to touch it again. BTW, the factory settings are close, but rarely perfect. That's why low end tuning is something everyone should practice, but few seem to do well.

The color of the oil on the plane after a flight is a good indicator. Lots of clear oil with white smoke while flying indicates a rich engine. As the smoke gets clearer, the engine is running leaner, and temperatures increase. Brown color in the oil indicates the oil is getting hot enough to start breaking down. A very light hint of brown is okay. Thats why having a little castor in the fuel is good. It won't break down as quickly, and will protect your engine better against a lean run.

Brad

Ok guys,

Thank you all for your great help. I sat down and read all of your advices.
I adjusted the engine so that when I run it up and down it does not hesitate and transitions smootly.I'm not getting any smoke at all from the exhaust,but all I see coming from the exhaust is tiny bits of oil.
I'm using Cool Power 10% and the color of the fuel is green. The oil on the plane afterwards is a little darker than the fuel.


Can someone tell me if everything is alright now?

Thanks a lot!

That sounds about right. Does it hold RPM when you stand it on its tail, or even better, pick up slightly?

Okay, it sounds like your getting close. heres the deal. You may still have a smooth transition but your setting s can stil be way off but we'll get to that in a while.

Factory settings! Don't need them and don't ever worry about getting things all fouled up and want to revert back to them. If you do want to start all over again, then do this. Find a quiet area with no noise (home). Open your high end about 3 turns and close your low end completely.

Now, remove the fuel line and attach a separate piece of fuel line to the carb, maybe around 5 ish inches long. Okay, at the same time, blow into the tube and open the low end needle until you hear a hissing noise. Congratulations, your low end is now in the ballpark and should be good enough to get it started up.

Start it up, generally, the high end needle is a no brainer, its the low end that causes all the problems. Once you understand the low end, you will have a nice RC career.

So start this thing up and dial it in as best you can. Low end/high end, get it where you "think" its good. Now how do you know the adjustments you made had an effect ? Smooth transition maybe but like I said earlier, it can still be way off.

Remember every time you make and adjustment on the low end, you need to check the high. You kind of bounce back and forth until it comes together.

So now you think yo have it and lets see if you do. Let the engine idle, while the engine is at an idle, carefully remove the fuel line from the carb and let the engine quit, if you cannot safely do this , thentake a pair of pliers and pinch the line until the engine quits.

Listen to the rpms as the engine quits, (this is very important), if the rpms increase a bit as the engine quits, your low end is too rich, this lean it a bit (1/turn at most). If the rpms just go down and quit, low end is too lean. I set all my engines for a very slight increase.

Also remember again each time to adjust that low end, check the high. There is absolutely no reason you cannot have a perfectly tuned engine and this is not a difficult task.

I reset mine at the beginning of each season due to temperatures and such and i do not have to reset my low end again for several months. It usually takes a couple tank fulls of fuel to get this done. This is a very easy thing to master. I have not had an engine fail on me in years due to tuning. Also with a perfectly tune engine, if something goes wrong, one thing for sue is that an out of adjustement engine is last on my list of things to look for. I know the engine is tune just fine so I look for other problems.

You will also find pilots who constsantly fool with their settings. this gives off the impression they know what they're doing, they don't and stay away from them.


As far as checking the high end, that tipping the plane up is pretty good. There is also a pinch method use for the high end, I rarely use it because most of my engines are enclosed. Basically, you run the engine full throttle, give the fuel line a quick pinch/release. Some look for a sligh tincrease in rpms and then back to normal, I go for no change.

Good luck

I recently purchased a nexstar and the limiter had been removed. I started it and the engine runs rough. Hesitation and then it will go to full speed and what seems like another pause during the climb.

After opening up this post I believe about a month ago I went and followed WTB's instructions and it roared into action. You just push it to full throttle then pinch the fuel line that goes into the cabureator for a few seconds and listen. If it speeds up your too rich turn high speed to the right, if it cuts out then it's too lean turn high speed needle to left. These are from WTB's instructions and I think they'll help you like it did me.

Good Luck!

I hate to spoil the fun, but the above (and very usefull) posts won't work until the limiter is removed from the carb. It won't let you either fully close or fully open the NV.

Ferocious -- if you feel brave, remove the limiter & start working your way through the info -- starting with the post from wtb3886.

If you don't feel brave, lean it out as far as it will go with the limiter in place (it won't hurt it a bit) & leave it there until your instructor actually "shows & tells" in detail, what you should do, & why.

Thanks for advice Britbrat,but I fixed my engine problem a long time ago. I believe rc pilot has the problem now.

I'll put an edit in the first post.

ll

Thanks for the advice Frankie, I was a little confused on which route to take. Im going to print wtb's instructions and go from there. Ill keep you guys posted.

Hey Frankie, If ya want your NexStar to really run good use Britbat's NexStar mods. I've only done the engine, pipe, & spinner part of his mods so far & I'm lapping my flying buddy with his WM Skyraider, I still need to make the cowl & turn it into a tail dragger, but just changing out the pipe & going to the 2 3/4 in spinner with an APC 11X5 has increased my power so much allready there isn't a Trainer at the Field I can't lap. & with the dihedral out of the wing I can get it to do all kinda stupid stuff that I have no business doing with a trainer.

Glad you're having fun Grump. Keep going. [8D]