I have an Evolution .46 trainer with the flywheel removed a 10x6 prop and 10% fuel. Engine runs great transitions good until about a half tank of fuel, then it wil die when ran up to full throttle from long period of idle. The fuel in the line will run back from the carb to the tank and it becomes hard to start without alot of priming. I switched to a glow with an idle bar and still the same results. Does anyone know the needle settings that I should start from? Any help would be appreciated.
Jamie

check your clunk in the fuel tank. Sounds like it may be stuck or fell off. Has it always done this? If so, then it might be the fuel line relation to the carburator. The two should be close to a straight line. Carburator inlet equal to centerline of tank. I would check the fuel clunk first.

Took fuel tank out and checked clunk and for air leaks and all is well. It is a touch lower than the remote needle valve but close, short fuel line from tank to valve. Everything is new except the engine which was prurchased used but in good shape. I did not know if maybe I had the vavle settings screwed up especialy the idle. Can you lose pressure from the exhaust that would let the fuel run back into the tank? Sometimes I have to cover the exhaust to build pressure tokeep fuel in the carb to get it started.
Jamie

The exhaust gasses passing through the muffler pressurize the fuel tank and push fuel to the carburator. It should not flow back to the tank with the engine running. Check the fuel line on the exhaust for leaks also.

When you cover the exhaust exit the pressure goes directly into the tank pushing the fuel up to the carb. I have to do this sometimes on the first run of the day.

Having the carburtor a bit lower than the tank is fine.

Doesn't the evolution have a blue anodized stop on the high speed needle? If your does, turn it as much counter clockwise as possible and then start to turn it clockwise until the engine peaks and then richen a few clicks. If the blue stops are gone then turn in until the needle stops and then back out two turns. The stock setting on the low end is 1 1/2 turns out.

You might have better luck with the OS A3 plug. </p>

The A3 is what was in it before I put the Idle bar glow in it. The fuel lines are new. I just bought a gasket set for the carb and I think O ring for the remote needle valve. I am going to try to repack the two and see if that helps. Been seeing bubles in the line after the remote needle so I thought that would be a good place to start. Thanks for the factory settings I think I may be a little rich on the low end, I will have to play with it after I repack and see where I am at.
Thanks for the help.

Hi there jamiebravo: I have The same Evolution engine, and it took me a while to get a handle on the needle valve settings. Through reading some RCU forums, I finally had all the mechanical needle valve restrictions removed along with the flywheel weight. Have quite a few hours of air time on the engine now, and have noticed a rich mixture in flight when going to half throttle. Another RCU discussion revealed that there is a mixture problem in the mid throttle range. The discussion commented on that after getting the high speed needle valve set properly, and the idle mixture set, that there was a rich transition from idle to max throttle. A couple of dead stick landings made me gun shy about lowering the idle rpm below 3000. My last trip to the club field, I lowered the idle to 2800 which seemed to be ok as far as becoming a deadstick pilot on final. Still the 10x5 prop and idle rpm makes for a high landing speed with my old heavy trainer. My high speed needle valve is set 200-300 rpms above the 4 cycle break. With added castor to my 10% Nitro all castor fuel, there is no problem locating the plane with such a smoke trail. I think someone suggested changing carbs to get the mid range mixture problem. I am using a Fox Miracle glow plug which is somewhat hot.

Let us know what you find fixes your problem.

Rich S.
A &amp; P mech

I think an Idle of 3000 is quite a bit high...<div></div><div>I'm able to get an idle around 2200 without nitro in my 46 engines (one magnum and one O.S FX)...</div><div></div><div>If your transition is rich....then your low needle is rich....the low needles control not only idle, but transition, that is the reason carb barrel goes in and out, they have a groove machined in a way to accomplish this, the more you close the carb, the closer the low needle gets to the spray bar (thus restricting fuel flow).</div><div></div><div>If I understand right what you say, you are closing the needle to get 200-300 rpm more from the 4 cycling..... that is definately RICH and definately not good for the health of the engine, not allowing it to come to operating temperatures.... high speed needle should be set ~300 rpm below peak RPMs...and then you adjust low needle. Unless is something wrong with something, you should be getting a niche idle about 2000 RPMS and a good transition if the needles are correctly set up.</div><div></div><div>Saludos,</div><div></div><div>Jorge</div>

I suggest to both of you also to reset the needle settinges, and try to tune the engine again.... Remove the stoppers of both needles....and look at the manual for an inital setting of the low needle, if there is any, then with the carb fully opened screw the low needle in a way that there is about ~1.5mm gap between needle and spray bar, it is a good starting point, and close to what my engines do when they are set.<div>
</div><div>Saludos,</div><div>
</div><div>Jorge</div>

The simplest and best thing to do next is to put in an OS A3 plug and retune. 

Since you got the engine used. Some people take the baffle out of the muffler for more power which would reduce muffler back pressure and also pressure to the tank. If after you try everything else and still not get it running right and find that the baffle has been removed. You can stick a little steel wool in muffler to increase back pressure. Shouldn't need much.

Never used the steel wool trick myself, but have read about it numerous times. Also have read numerous times about the baffle being removed in that engine.

Hope you find the issue. They are a decent running engine. I have one, but haven't modified it yet.

Good Luck

I have gone through the fuel system and found no leaks.  I replaced the 'O' rings in the carb and remote needle.  I have isolated the fuel tank from the airplane with foam. called the manufacturer about needle settings. Put a deflector on the muffler to increase back presure.  Adjusted the needles till I had to replace the 'O' rings again.  Put a glow in with a idle bar and still have problems with it going from low to high rpm.  I t will just die. If you run it at low or mid throttle for awhile and go to full throttle it wil die. I had a plug with a 'H' on it and tried it no help.  The engine is on a Uproar which puts the tank pretty low when compared to the carb so I am thinking a different engine....?  The engine will run good and transition good then start in with the problems after about a minute or two.  I may try the steel wool to get more pressure.
Any other ideas

I was reading the manual on line and it said that if the engine runs poor one of teh problems could be bad fuel.  What the heck I had a new jug why not??? It runs alot better, I was able to run a full tank installed in the plane without it dieing on me.  The other jug of fuel was not that old so I did not figure it to be bad (Wildcat 10%).  I still have a problem where if I let it idle for a minute simulating an approach, the engine seems to load up and want to die if you go straight to full throttle.  Did the pinch test on the low end and it is good where it is. I could lean it alittle more but then it seems that I have to richen the high end to make up for it.
Thanks for all the info. This has been frustrating. I would rather be flying.

BLW,
I forgot to say I put an A3 in it and tried retuning, I am not sure if I am quite there yet.  What is the difference in being to lean or to rich on the low end? Sound, RPM, Hesitation...