I just made my first flight w/ my Nextstar last Saturday. After about 5 minutes of flying, the engine just quit. My friend took over w/ the buddy box and brought in safely. After inspecting the plane, I saw the exhaust deflector fell off sometime during the flight. Would this cause the engine to quit. We coudn't get the engine to run w/o the deflector and I didn't have a spare. ( BTW the engine is an OS 46 FXi and I'm not sure about the muffler. Whatever came w/ the engine.)

Also, I couldn't get the fuel to drain from the tank when I was packing up.

When I got home, I took the engine off the plane and removed the fuel tank. I couldn't find anything wrong with the tank or tubing. When I reassembled everything. I decided to reorient the muffler away from the plane a little more.
When I took apart the muffler, a cone shaped plate fell out & I didn't notice which direction it sits in the muffler. Is this the baffle? Does it point towards or away from the front of the muffler.

I know there's alot of questions here, but any help is appreciated. Thanks.

OK, sounds like the long screw down the middle of the muffler broke. This is common with OS engines/mufflers, at least in my area. OS has told me that it is caused by the casting expanding more than the screw,when hot, and snapping the screw. They blamed me for overtightening the screw even though I had never touched it and basically said "too bad, buy another muffler from us". The muffler pieces are not available separately except for the screw/nut assy. If you have lost the back piece, you will have to find one on your own or replace the muffler entirely. The disk that fell out IS a baffle and although it usually dishes to the front (I think) I've seen it both ways. If you get a new muffler, go to Home Depot and get a piece of 6-32 All-thread rod and a couple of metal locking nuts to fit. Cut the rod to the length of the muffler and replace the screw with it. Use a nut on each end. You will have to drill the muffler hole open just a bit for the rod to fit. Several of us use this trick and have never had a failure of a muffler modified this way.
The engine doesn't like to run without the muffler because it is tuned to run with the backpressure to help keep the glowplug hot.

Oh the screw didn't break. I lost just the silicon exhaust deflector, not the whole muffler. When I was back home, I took apart the muffler and dropped the baffle before noticing which way it pointed.

I want to know
1. if the deflector will affect the engine running or not. I've already replaced it, I'm just curious.
2. any suggestions about the fuel tank.
3. which way the baffle needs to be pointed if it matters.

Thanks.

1. Shouldn't.

2. Did the clunk get flipped forward on landing? You should be able to remove the line from the needle valve and pump the fuel out thru that line. Make sure that is the clunk pickup line. Sometimes people get the lines switched. Fill tank and the drain completely. If problems occur, remove tank and resolve problem before next flight.

3. Don't believe it really matters but I think dished forwards. When replacing the screw, just lightly snug it down until back of muffler will not turn.(Do not overtighten) Then install jam nut on rear. (This is procedure given me by OS.)

1. Thanks. I didn't think so either, but I know backpressure can be important to 2 cycle engines & I didn't know how much the deflector would affect this.

2. Doubt it if the clunk did get flipped because I was flying level making gentle turns when it cut out. My buddy said we should have heard a difference in the sound of the engine if it ran out of fuel or got starved. We didn't. Nothing spectacular happend in the landing. My friend made a great dead stick landing.

3. I've already reassembled it w/ the baffle pointing towards the rear of the airplane. I'll ground check the engine before I fly again and change it if need be. I'll be sure to check the tightness of the screw before I run the engine. Good tip to know.

Thanks for the help.

I know the problem well you probaly lost the deflector early on but that didn't kill the engine the clunk or tube fell off in the tank. that is why you can not get fuel out of the tank when the level is below the brass tubing that goes through the stopper and why the engine stopped at 5 minutes. half the fuel is gone. open the tank and inspect the clunk and fuel line for leaks in the tank.

Make sure you are drawing fuel from correct line. If drawing from vent, it would fly for a bit and then suddenly quit. Additionally, you would not be able to de-fuel.

Gotta leave work. Good luck.

I did inspect the tank while I had it out of the plane, but didn't see anything obvious. You are the second person to mention something like that though. I'll have to take a second look. while I'm in there I may as well replace the tubing too. Thanks.

remember we said inside the tank. looking at the outside will not show the failure.

Any chanch you had the engine adjusted a bit on the lean side?? Especially a new engine will sometimes quit after a few minutes run if it is too lean. I use the OS 46's and usually run them slightly rich. ENJOY!!!! Red

The deflector will affect the engine. The backpressure is greater than with the undeflected muffler, which makes the engine run richer than usual, thus requiring you to lean out the mixture to run correctly. The loss of the deflector will reduce the backpressure & instantly lean the engine out. If you had it a hair on the lean side to start with, it could kill the engine in flight, particularly if you were at full throttle when the deflector came off.

Hi!
1. The deflector will not affect engine setting if you just used the commercial short coloured ones of silicon with a 45 degree bend.

2. Did you use a 8-10 oz tank..you should. Did you do the sucking tongue test before mounting the tank in the airplane...you should. Did you pad the tank with lots of soft foam...you should. Did you use fuel containing 5-10% nitro...you should. Did you use a balanced 11x6 or 12x4 APC prop..you should. Did you use a proper glowplug for your engine, an OS 8 or Enya 3.
Did you set the engine a little rich before you took of...you always should. Did you hold the nose of the plane up checking the engine setting before first take off...you always should.
There you are....happy flying.
Regards!
Jan K
Sweden

I beg to differ about the exhaust deflector. An exhaust deflector can cause a change in the back pressure of the engine. Some engines won't tolerate much added to the muffler...even ones with a very small curve. Since the Hobbico NexSTAR doesn't come with an exhaust deflector, one must have been added. As was stated above, this does change the pressure relationship of the muffler and tank. Even when properly-leaned, an exhaust deflector can add just enough additional back pressure that the engine will gradually overheat and then quit. Most of the time, though, no damage happens to the engine.

The cone inside the muffler should be oriented with the wide part forward, coning in towards the rear.

When I had the plane apart ( ie: muffler off, engine off and tank out ) I took the stopper out of the tank and inspected the insides. Didn't see anything there. Did notice I need to tip the plane nose down to de-fuel effectively though. Reassembled everything. Installed a new deflector. Started it up last night and it fired right up. Adjusted the needle so it was running just slightly rich. Engine seemed to run fine. Also de-fueled it to about half full. (About the level it cut out while flying @ the field.) Ran fine there too. De-fueled it further and still ran fine.

Am I missing something or is it OK to try again?

P.S. to JAKA

The tank is 250cc. About 8.5 oz. Sucking tongue test??? I'm new to R/C planes. I'm not sure what that is. Can you explain that? The plane is an RTF NextSTAR. There is some foam, but I wouldn't say lots. Using 10% nitro fuel. The prop came w/ the plane & is 11X5 nylon. Glow plug is A3. Engine is set slightly rich. What does holding the nose up & checking the setting do for you. What would I be checking for?

Thanks for all the suggestions and tips. It's great to have such a source of info.

Bax

I did reassemble the muffler w/ the baffle & I did orient it as you said. I had a 50/50 shot. Guess I chose correctly. Just makes me feel better knowing its right. Thanks for answering that part.

Are you saying exhaust deflectors are a bad idea? Or just that the engine needs to be tuned accordingly? (ie: as you plan to fly, either with or without a deflector)

Should be ok to try it again, especially since you set it slightly richer. Mine seem to like to run a click or so rich. Just a thought since you mentioned the fuel tubing inside the tank, and had problems with it cutting out in flight and defueling... Is it possible that you may have a hole(pinhole) or even a cracked piece of fuel tubing in there somewhere? Possibly not noticeable on the ground, but maybe vibration and forces in flight just enough to release the pressure in the tank. Seen it happen once or twice, might be worth another very close look at the tubing...

Jaka's advice is all good, and exactly right. I am however, wondering what the "sucking tongue test" is also... never heard of that one before either! (15 years of flying)

When you tip the plane up while running, you're checking to see if the motor leans out or quits. If it does, then you need to adjust your needle or fuel tank setup so that it runs consistently regardless of orientation. This will also tell you wether your clunk has shifted to the front of the tank without having to take the tank out of the plane and take it apart to see.

Good luck! [8D]

I know what he's referring to, but I don't recommend it. He's sucking on one tube from the tank and holding his tongue over the tube to see if the tank leaks. I don't recommend it because I doubt anybody here would enjoy sucking up nitro fuel. yuck!!!!

Let's go thru one thing at a time.
1. Should not have to point nose down to drain, nose up if anything to get last drop but level should be good enough.
The fuel lie that feed fuel to the engine should be attached to a flexible line in the tank. The flex lin should extend toward the rear and have a weighted pickup on it. The end of the pickup should come approx 1/8 to 1/4 shy of the back of the tank, definately not in contact. The purpose of the weight is to stay at the bottom of the tank in whatever attitude the plane is in and maintain continuous fuel draw. If fuel draw is being interrupted prior to near empty tank, something is wrong. Even a very small pinhole in the pickup line will allow air into the line and kill the engine
2. The tongue suck test- Haven't heard quite that before but basicly it is this. Squeeze the vent line tightly shut and suck on the carb line. Jaka then wants you to put your tongue over the end of the line and see if the unit maintains vacuum. I prefer to cap the vent and place tank underwater and blow into carb line and look for bubbles. Looking for tank leaks here. Neither of these will spot an internal leak though.
3. Tank and prop you have are fine as long as they are in good condition.
4. 10% is good
5. Glow plug is good type.
6. May need to adjust idle mixture at later date, not a concern just yet.
7.With the engine tuned "just off peak" like you have been, by raising the nose you are making sure that the change in attitude and relative position between tank and needlevalve is not going to over-lean the engine. If there is no loss of power all is fine. This is done at full power.

Next?

Jaka, if I guessed wrong at your technique, please correct me

OK my tank has 3 lines coming out of it. One leads to the needle valve and on to the carb. One is the pressure line leading to the muffler. And the last is the fuel, de-fuel line. On the other side of the stopper of these lines is this:

ON the carb line is a short piece of tubing w/ the clunk. It's oriented as you said.
On the pressure line is a short piece of metal tubing that curves up towards the top of the tank.
On the fill line is a short piece of metal tubing that curves up towards the bottom of the tank.
That's why I said I need to tip the plane nose down to drain more of the fuel.

I bought the plane off E-bay. Seller said he never flown it so as far as I know it's only made two flights. When I got it I ran a tank of fuel thru it per the instructions to break in the engine. Nothing suggested a leak, but I can't guarantee that there isn't one.

I'll try to check the tank and tubing for leaks and see what happens.

Do you have ready access to where the fuel line attaches to the needle valve?

"On the fill line is a short piece of metal tubing that curves up towards the bottom of the tank. "

It can't curve "UP" to the "BOTTOM". Which is it?[sm=confused.gif]

Is the "fill" line left open or capped/plugged during flight?

I have access but very good. Its right next to the engine.

Sorry that was a typo. It curves down toward the bottom. Right near the front of the tank & plane. Thus tipping the plane nose down helps w/ de-fueling.

The fill line has a plug and it was in during flight and ground running.

I don't personally like 3-line systems but they work. Seem overly complicated on a simple plane like this with exposed engine. With that said, that does explain the tipping to drain tank.

Assuming there are no holes in the linesand the stopper is tight (don't over do it) it should work the way it is.

Check the lines or spend a buck and replace them and try it again. Make sure you don't have excessively long lines going to the needle or from needle to carb. Slack should be kept to minimum without crimping/pinching

It all depends upon the engine. Some engines won't tolerate anything added to the stock muffler. Other engines don't "care". If you wish to use a deflector, you may need a larger exhaust outlet on the muffler, which then takes a deflector with a larger inside diameter. It all adds up to the amount of back-pressure seen by the engine. An exhaust system that's as 'tight' as possible to help keep down noise, or one that's finely-tuned to the engine won't tolerate much added to it if there's the slightest bit of added back pressure.

Assuming everything checks out OK and you can't isolate the problem, I'd suspect engine tuning problems. First, have you run the engine on the ground to break it in? I believe NextStar says the engine is broken in, but I wouldn't believe their claim. I'd run a couple of tanks of fuel through it to ensure its reliable operation in the air. Next make sure the engine is set on the rich side. Max engines won't run reliably if they are lean. After every flight move the needle valve in a click until you reach what Max calls the optimum RPM. This is 15-30 degrees away from the maximum RPM (Where the engine is leaned out for max RPM).

Incidentally, I own three OS engines: 40LA, 46 AX, and an old 19. All of them run great, and the 40 and 19 have had many gallons run through them.

Ciao,

Eagle Al