South Land Aero Modelers

As I was flying today, I kept having problems with my engine (Evolution .46). It would start just fine, but most of the time I could not keep it at full throttle for more than 30 seconds (engine would die). I adjusted the trim multiple times (tried it both too lean and too rich - and of course in the middle), but nothing seemed to work. I did finally get the engine to work for a short time, but each time I pulled back hard on the elevator (going into a loop), the engine would greatly slow or die (I had about three dead stick landings). Flying inverted was fine, so I don't think it's a gas tank issue. When I got home, I continued to try and tune the engine, but again, nothing seemed to work. Most of the time, in order to go from idle to full throttle, it was necessary to very gradually push up on the stick... and even then, once full throttle was reached, it would die within a minute (unless I pulled it quickly back to idle... in which case it would run fine). Not sure if any of that makes sense, but if anyone has suggestions I would greatly appreciate it.

By the way... it was a wonderful day to be at the field... near perfect weather and very little wind!!

In Him,
Wes

Floyd, what is your take on this situation? My first guess was fuel clunk. But flying inverted threw that out the window. Is it too lean?

Check for air leaks around the carb and back plate. Look for pin holes in the fuel line. If that is all fine then change the glow plug. You could also have bad fuel.

Just an update... I've checked the gas tank... seems fine (the plastic cap around the opening was broken, but I took it off and the rubber stopper still seals the hole just fine), I've replaced the fuel tubing, cleaned out the muffler (which was fine), and replaced the glow plug. After all this I still had issues. Engine cranks just fine, idles great... but still struggles to maintain high rpm. It is possible to get the engine to maintain a high rpm (by gradually increasing the throttle), but when I go quickly from idle to full throttle, it wants to die. The only thing that seemed to help was taking off the restrictor pin on the high speed adjustment, and going past the factory recommended settings (going counter-clockwise past recommended setting). Something else I noticed was that the engine performed better when cold... after warming up for a few min., the problems were more pronounced. Still working on it... let me know if you have any clues - thanks.

In Him,
Wes

Didn't about Wes's problem till Saturday when he came out while Bart and I were there. The main needle valve has little effect on rpm, but I did hold it nose up and leaned it out until it peaked then off a couple of clicks and he flew it most all afternoon with out it cutting off, BUT he said it was surging while in the air????? It has a 3 blade prop and maybe that loads it a little? Came from factory with it though.

The plane did fly a lot better on Sat... thank you Floyd and Bart for the help. The issue seems weird to me... the engine will run fine for 5 - 8 minutes, and then all the sudden struggle to maintain rpms. To temporarily solve the problem (in mid-air), all I have to do is pull the throttle back to idle, and then gradually increase back to full throttle. Others have had this same issue (I found several forums regarding issues with the evolution .46)... One suggestion was to use an OS A3 glow plug b/c it's hotter (I've ordered one), but I'm not convinced that's the problem. Floyd suggested that even though I replaced the fuel lines, there could be a small hole in the fuel tube on the inside of the gas tank (I didn't replace that one)... this could explain why the engine runs fine for the first 5-8 min, and then after the fuel level has decreased, the hole in the fuel line is exposed and causes the problem... I'm going to replace it before going out next time. Anyways, any other suggestions are always welcome... by the way, it was a great day to be out at the field!!

Wes

Wes,
Before you take the tank out to check for a leak, maybe just try to run the engine on the ground with maybe 1/3 of the tank full. I imagine you probably thought of that already, but just in case...

Nick

Not quite sure yet... I replaced the fuel tank (I noticed just a little bit of fuel leaking around the seal, so I just bought a new one), and I've replaced the glow plug with an OS A3... brian's got me a new two blade prop (instead of the factory three blade)... I got a new prop b/c someone suggested that the three blade might be messing up the air flow for the carb., plus I wanted to add a bit of speed. I'll prob. test it later on this week... I'll let you know what happens. If I had to bet, Floyd's theory makes the most sense to me (leak on the inside of the tank) - I'll post an update Fri. night.

Just giving you an update... I went out to the field today (Friday morning) after making some adjustments to my Evo .46. I've replaced the fuel tank, the glow plug, all fuel lines, and I just put on a new high speed needle valve adjustment. Guess what??? Still having basically the same problem, although it doesn't seem as bad. I also put on a new 10 X 6 prop and was absolutely amazed at how much the power and speed increased!! But after everything, the engine still struggles to maintain high rpms. No problem at idle or half throttle, but at full throttle the engine will "pulse" from high rpms to mid range rpms - and if I leave it at full throttle, the engine will die. I've about decided to take Shannon's advice and just live with it until I get my next plane (hopefully pretty soon). I've been told that I probably have an air leak somewhere, but I can't find anything. By the way, it was very windy this morning... almost didn't fly, but then said "what the heck" and flew anyways... ended up being a great morning. As always, any advice is appreciated.

Just a thought... my dad was having sort of the same problems with his new Super Tiger. Now I don't know much about the Evolution motors, but his low speed set screw was adjusted wrong and leaning out his top end. It would fluctuate like your saying and would just die out at all RPMs, very randomly. Do the Evo's have an idle set screw? And if it's anything like my dad's, his was REAL touchy. Not even a minute turn of the screw would make it go all crazy. Hope this helps.
Chris

Edit: I also found this that sounds something like that...
http://www.rcuniverse.com/magazine/arti ... cle_id=153

How does your fuel line attach to the muffler? is the nipple tight and not stripped out? It almost sounds like a pressure problem or maybe you are getting a lot of foam in the fuel tank. It sounds like foam to me. I assume the tank has foam wrapped around it? Is your propellor balanced? There has to be a cure!

Joe S has rubberbanded a spare tank on the outside of the fuse to see if it was tank height or not. Must be secure.
If its still under warrenty, send it back, this is to much for a new engine. FloydR

Hey... quick question... How do I keep bubbles from getting into the fuel line? Here at the house, I've noticed that at idle there are no bubbles in the fuel line, but as I increase the rpms, bubbles start to show up... and at full throttle, a whole lot of bubbles are going through the fuel line. As a result, at full throttle, when the bubbles are going through the carb., the rpms decrease dramatically. This may be my problem... let me know the best way to remedy this issue. Thanks.

Could be the vibration from the engine. Tank is wrapped in foam and the prop is balanced?

Aha. Bubbles in the line. Possible causes are the tank shaking around at high RPM and check to see if your fuel is foaming in the tank at full throttle. Another idea is you're getting too much pressure in the tank. Try to set the fuel tank higher than the motor and disconnect the pressure tube. If it runs better then I would say that may be the problem (too much pressure). You can also get another fuel tank like this one...
http://www.centralhobbies.com/Fuel/fueltnk2.html