snicky

I could use some help with my Evolution .52NX Glow Engine. It runs fine when I first start up and on the ground. I've performed the pinch test and the hi-speed valve seems to be right. Once in flight, everything seems fine for a while until the engine seems to warm up. Hi-end runs fine but when I back off on the throttle and re-accelerate the engine dies. I've pressurized the fuel tank and check the lines for leaks and can't find any. Using Omega new fuel. Any suggestions?

flybyjohn

My Feedback: (2)

Have you started it on the ground and after warming the engine up, bring it to idle and let it sit for about a minute and then go to full throttle as fast as you can? This is a test for low speed needle. If it burbbles and then dies or picks up rpm then it is a little rich, if it just dies then it is too lean and if it just picks up rpm without much burbling then it is just about right.

Pete Bergstrom

It sounds to me that your low speed needle is set too lean and the engine is quitting in the transition. Try richening the low needle

Pete

RCPAUL

My Feedback: (1)

Or, a little fuel foaming?

aspeed

Motors do lean out at the end of a tank too.  One or two clicks richer on the high speed needle may solve this.  You can maybe check this by filling the tank half full when making your initial settings.

luvtoav8

I've had that problem when using fuel with too high nitro content. The solution was either to add an extra head gasket or shim or to use a lower nitro fuel like 5% or FAI. The Tower Pro and GMS engines came with an extra head gasket to correct this problem back in the days they were available. I've also experienced the problem with older Fox engines. I always just went to the lower nitro fuel. I experienced the problem mostly in the summers here in Virginia which can be hot and humid. The engine is essentially over compressed.

snicky

Thanks for all the advice. I'm wondering if somehow the low-end got out of wack and is running to lean as you suggest. Last year when the engine was new it seemed to run fine. In the Fall I moved the engine to another plane and it has been problem ever since. (10 flights w/8 engine kills) From the manual, the low-end needle valve on the EVO includes a"SetRight" mechanism with what appears tohave a slider which has a limted movementclock orcounter-clockwise.Would I be correct is "to rich'n low-end I slide or turn counter-clockwise"?. If it doesn't allow enough adjustment I might have to go outside factory parimeters.

iskandar taib

My Feedback: (5)

Perhaps you mean it DIES in flight..

Tried changing the plug yet?

Iskandar

blw

My Feedback: (3)

Evolution 2 strokes are a little different than others. They love nitro so don't worry about that.

The set right is only a limited range for new guys to use. You can either remove the collar limit altogether, or loosen the set screw to give you either more rich or more lean to work with. You tighten the set screw and then fly with your new limited range of adjustment.

Do this test. Crank the engine and slowly advance the throttle as it warms up. Does it seem to gurgle on fuel. Does it sound wet when it runs rough? Also, check this out when it is hot with slow advances and faster ones. This is a sign of the plug being too cold. All of the Evo 2 strokes that I know about have this 'feature'. If not, then I would richen the low speed needle and repeat the first checks. The OS A3 plug is about right. The OS 8 is too cold for sure.

For general info, I bought my first Evolution years ago. It was the TPS .455 and I've run the living snot out of it, and so did the original owner. Actually, he abused it. I finally took it apart for new bearings and found that the first owner had taken out the two head shims way back when. This engine has a ton of power with the higher compression. I wonder what my .46NTs are going to do without the shims.

snicky

Yup, dies in flight. I can't get it to kill on the ground. I said previousl it seems to run file for the 1st part, then after you back-off on the thoittle it dies when you attemp to re-accelerate.

snicky

I'll give your advise a try "blw". Between my son and I, we have 2 mor evo .52NX and they run flawless. This one is my sons and just really been a problen since it was moved to another plane. I really think as most everone says, the low needle setting being too lean.

1QwkSport2.5r

I'd verify there are no bubbles in the fuel line when running it up and down as well. Air bubbles are notorious for causing an engine to quit.

jaka

Hi!
Some questions?
How high is your tank sitting compared to the carb?
What size is your prop?

blw

My Feedback: (3)

Snicky,

I've set low speed needles to what I thought was just right only to have the short test flight around the field show that it was too lean many times. Flying will make a lean setting show up. I don't use the pinch test or hold the nose up at full throttle.

Another peculiarity with Evolution engines- they use the worst, cheapest fuel tubing from the remote nv to the carb.

spd101

low speed needle, ive got 2 46's and the new .91 and they are all great

tlojak38

My Feedback: (15)

blw, never thought about taking the head shims out, (wondering what that will do to my evo .61). is it harder to tune? im using an A3 in it right now.

snicky

Again, thanks for all the tips. Last night we worked on the low speed needle to no avail. Tried the "let idle for 1 min. and punched it method" and it immediately killed. The .52nx is installed in a Hangar9 Twist with factory fuel tank and location. Although I've been wrong numerous times on what I think the problem is, since we never had the issue originally and the engine ran fine, I don't think it's the low speed needle. It probably is now after I messed with it :-(. I'm seeing air bubbles in the line and I am suspecting an air leak. I think I'll remove the engine and fuel tank, check tightness, and replace ALL fuel lines and test run on engine stand. If the I don't find an air leak, do you suppose it's worth looking for dirt in carb, etc.? Should I consider disassemble of carb. for cleaning?

1QwkSport2.5r

Bubbles in the fuel line is from either bad fuel plumbing (probably inside the tank) or fuel foaming from vibration. Check the balance of the prop, and ensure the fuel tank is heavily padded with dense foam. Of course this is only after replacing all tubing inside the fuel tank.

If the fuel tank cannot be padded due to lack of space, swap fuel tanks with a Tettra or BubbleJett fuel tank.

Pete Bergstrom

Seeing that the engine was running fine on a different airframe and now does not I would agree with others that there is an issue in gettting the fuel to the engine. I know on our Twist there is not a lot of room for foam padding around the tank and the likely candidate seems that the tank is foaming the fuel after it reaches a certain fuel level. We came up with this in-tank fuel filter/clunk to get rid of the air bubbles that like to work their way through the lines. Give one of these a try and I think your issues will go away.

http://www.evolutionengines.com/Prod...ProdID=EVOA106

Pete

fly24-7

While you're looking at your plumbing issues, you should probably set the needles back to factory settings and start the tunning process again. The problem you experience does sound symptomatic of the low speed needle setting. If it's too lean, there's fuel starvation in transition and it'll die. If it's too rich, the glow plug can get quenched with fuel in transition and it'll die. In between, you get the roughness and hesitation until it's dialed-in with the correct metering of fuel. It's not uncommon to see some differences in performance in the air as the loading on the engine is different than when you have the plane restrained on the ground.

I have the 52 installed on a Kaos 40. It ran a little eratic during the first 6-7 flights and then settled in after that. Runs as good as the EVO 46 engines I have. Run Omega 15% in all of them. Good luck...

iskandar taib

My Feedback: (5)

Taking out the shim(s) would increase the compression ratio. This would allow you to use less nitro (or no nitro) but it might cause pre-ignition and overheating (not to mention blown plugs) with high nitro fuels.

Competition pilots will (once the engine is broken in) decrease the thickness of the shim(s) until plug life starts to suffer, and then add a little thickness.

Iskandar

aspeed

I think if you are idling for one minute, and expecting it to accelerate to full bore, that you are expecting too much.  Any motor will cool off and most will quit IMHO.  Same as the first 30 seconds of start up.  The motor should be run full blast to get some heat into it before expecting a reliable idle.  Most motors are designed to be run full out  or at least close to it.  Otherwise, as has been said already, if it stumbles, the low speed needle is rich,   if it just quits, it is too lean.  It may also need more compression in some cases to keep lit. Such as cool air, low or no nitro etc.

blw

My Feedback: (3)

Air in the fuel line will do it. I just had that problem not long ago with an old tank.

Some common problems could be a hole in the fuel line section inside of the fuel tank. Cracked brass tubing going thru the stopper. Leaking stopper. W8YE said that a cracked brass tubing once gave him fits until he found it.

Iskandar- I think all Evos will take a lot of nitro. I've seen them run 50%. I'm taking the shims back out of the TPS engine the next time I run it. It always ran on 15% to 30% nitro.

The two Evos that I fly- the .46NT and TPS .455 will take a 25 - 30 second idle and then transition well to full throttle. The .455 without shims would take it as fast as you could shove it full throttle. I heard about this technique from someone else on RCU.

1QwkSport2.5r

A felt clunk will not cure bubbling fuel! I have tried felt clunks and sintered clunks to no avail on several engines. TT .46 Pro, Super Tigre S90, Super Tigre S29, and a Jett .35. The felt clunk would not flow enough fuel for the S90. The engine ran lean with the needle OUT of the carb completely! The cure was using a bubbleless tank on all four engines.

If a guy wants to try a felt clunk anyway, try a small engine shop or Ace hardware. They're about $3-4 at Ace. You have to use a Dubro or Sullivan tanks as those felt clunks will not fit Hayes tanks.

snicky

Now that I probably messed up the low speed needle, anyone have any suggestions what the factory setting should be? I think the hi speed needle is real close to right.