Evolution PTS at Altitude - Issues, Please Help!
 

Hey everyone,

I'm trying to get back into flying with a trainer i bought a few years ago. I bought a new Evolution PTS since i heard they are a very reliable and fairly good performing engine for the size plane I have. Well, I am having a real hard time understanding what the heck is wrong with this thing. Here is the youtube video i posted so that folks can hear the issue. http://youtu.be/lid7UyG8wtY

If you have any recommendations, i would really appreciate it. I cant feel comfortable putting this thing in the air given the way its running. Id like to eventually strap a GoPro to it for some footage, but i need something stable first.

I had a to back it off once in the video because it would have stalled.

Thanks in advance for your help!

RE: Evolution PTS at Altitude - Issues, Please Help!
 

What fuel are you using (nitro and oil %), what prop, what glow plug, and what kind of weather (temp/humidity)? For the most part, from the video, it doesnt sound like its too far off though at the end of the video it sounded a little funky. Almost sounds a little lean.

Also, what is the procedure you've been following to tune the engine?

RE: Evolution PTS at Altitude - Issues, Please Help!
 

I followed the procedure in the manual; pinch the fuel line and adjust according to the behavior. Im using 15% nitro, standard glow plug that came with the engine. The weather was gorgeous: 70 degrees, sunny, low humidity. its colorado, its always low humidity :)

Thanks!

RE: Evolution PTS at Altitude - Issues, Please Help!
 

I'd suggest trying another glow plug; break-in is hard on glow plugs. You did break the engine in on a test stand first, right? I wouldn't think of running an engine on a plane in flight without having at least a quart of fuel run through it if ABC/ABN/AAC and 1/2-3/4 gallon if ringed. If the engine is not broke in well enough, its probably getting hot from friction and needs more run time to loosen up and be less finicky. Some engines need to be extra rich for the first few flights until the internal parts bed-in.

If you dont know what glow plug is in it, you should find out. Being in the higher altitude, the 15% nitro will help it run better, but might need a hotter plug to stay lit in the thinner air.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Yep, I put a good quart or more through it on the test stand before flying. During the first few flights, it worked OK but I could definitely tell there was something not quite right with it. As you can here in the video, the RPMs are all over the place at 3/4 throttle. I only backed it down once, every other change in RPM is the engine.

I'll see if I can get a new glow plug for it and try that. Any other suggestions? Leaner, richer?

Thanks!

RE: Evolution PTS at Altitude - Issues, Please Help!
 

The biggest problem is that it will not go past 3/4 throttle without either dying completely or fluctuating in RPMs. i can't tune it because no matter how lean or rich i put it, it wont go past 3/4 throttle.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Something is restricting fuel flow. If it will die past 3/4 throttle, and richening the needle does not change how it runs and sounds, then you need to find the restriction. Something isn't right.

When an engine surges, its a sign of lean mixture. Ensure the fuel tank centerline is dead even with the centerline of the tank or the tank ever so slightly below carb centerline. This is important, especially if the engine has a large bore carburetor as fuel draw will be poor. Ensure the pressure fitting on the muffler is clear, and make sure the fuel tank's pressure port is open/clear.

On the engine, its not a bad idea to pull the carb off, disassemble, and inspect. A piece of debris could be restricting fuel flow. If carb is clean and good to go, reinstall on engine pushing down hard on carb to seat against o-ring well and cinch the bolt down. Next, open the main needle 1 turn from where it is now, and open the idle needle 1/2 turn from where it is now. This will probably require starting at part throttle. Run the engine to WOT, and lean the main needle down just until its running in a clean 2-stroke tone. If its missing occasionally, lean it until it quits missing. (note how much it takes to go from rich to lean. You should get at least 1/2 turn or more from Rich to Lean.) Now adjust idle mixture for clean transition. Make sure you're not idling too low or too high. 2500-2800rpm is where I like my engines to idle, and is where I usually find the transition to be the best. Once the needles are set, run to half throttle and listen to the engine. If it starts to load up or surge, adjust the idle needle accordingly until it clears up, and drop back to idle. Adjust idle rpm if necessary. If none of this works and it still misbehaves, try a different prop. Perhaps its over-propped, OR you may have a fuel foaming problem. watch the fuel line to the carb while doing the tuning at as high of an RPM as possible, WOT is best obviously.


Make sure the cylinder head and backplate are tight and leak-free as well. Maybe pull the tank apart and check the clunk line for a pinhole or cut too.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Nice. I'll give these a recommendations a shot and report back. Thank you very much for your help. It is greatly appreciated.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Where there's a will, theres a way. Something is amiss and the process of elimination is about the only way to track down the culprit. Good luck.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Hi!
You are running it too lean! Listen to how the rpm drops and fluctuate...

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Jan, if you read an earlier post, he said no matter how rich or lean he turns the needle, it still acts up. I think it sounds like its more than just a needling problem...

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Yeah, i can rich it out to where its spewing dropplets of fuel and smoke, and it still acts the same.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Well, you should always have droplets (albeit small) of oil coming from the exhaust at all times. If you can unscrew the needle and almost remove it from the carb while the engine runs and it does not richen up so much that it 4-cycles and drops to 5000rpm, then you have a fuel restriction without a doubt and have to find that restriction.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

I had my PTS Evo 45 on a Xtra Easy 2 too, and it is my favorite 2 stroke. I just replaced the bearings after many hours of hard running, and it looks new with a crockpot cleaning. It stills puts out good power on 15% and APC 10x6 or 11x7 props.

You can hear the wet sound as your engine transitions from idle. This how the smaller Evos run when using a glowplug like the OS 8. This is too cold for the engine. Your first thing to do is get an OS A3. This is a hotter plug and you will pick up a lot of power, and end the stumbling, rich condition you hear on the video as you accelerate rpms. You will probably be able to richen you low speed and high speed needles since you have cured the Evo cold plug issue.

Evos have the worst fuel tubing in the world between the remote needle valve and carb. They leak air. I've replaced that on 8 or 9 Evos.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

I had an Evo engine in my brand new PTS Mustang Trainer when I started out and all it did was teach me how to land dead stick. I don't want to bash but I ended up replacing it with an OS .46 and never had another problem. I have seen some guys get good ones but any time I talk about my experance I have gotten conformation from other pilots that more of these engines are bad than good. Mine had the blue collar that "is set from the factory for sucess with only minor adjustments," not so much. When you are done fiddleing around with it and provided you haven't crashed your plane swap it out. My comments are based on what happened to me I had everyone even a guy who rebuilds nitro engines try to set it and it never ran correctly for more than 1 flight.
Good luck. 

RE: Evolution PTS at Altitude - Issues, Please Help!
 

It's too lean.

So if what you say here is happening, look for an air leak. The usual suspect locations are the seal between the crankcase and the carb and the backplate on the crankcase.

Some engines will not run worth a hoot on some brands of fuels wheras other will do just fine. Same thing goes for glow plugs. And virtually all engines run poorly on old and moisture contaminated fuel.

Break in is a critical time. The procedure differs for ABC and ringed engines. And in neither case does it mean just flailing the crap out of it at wide open throttle.

It's also not a good idea to have it wailing away at wide open throttle for an extended period of time on the ground. It will easily overheat. It gets better cooling when flying.

Overheating, too lean running and improper or not breaking in will destroy any engine in short order. Following that, it doesn't matter what you do to it. You'll solve your problem by replacing it, starting over and avoiding the killers.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

That engine is sucking air.
Evos ( especialy the .45 and .46's) had a problem with coming from the factory without an oring under the carb. Might check that.
OR might be just a bit loose.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Hi!
When I look and listen to your video It's very obvious that the engine isn't getting enough fuel.
Have you tried open the needle some more at full throttle?

Your engine is screaming at full throttle and is on the brink of stopping and you do nothing...Why don't you open the high speed needle?;)

RE: Evolution PTS at Altitude - Issues, Please Help!
 

I didn't see any smoke at all in that run. Exhaust deflectors sometimes raise havoc in tuning, so try it without. The high speed needle should be very controllable on these engines. In other words, you should be able to go from too rich to too lean in a half turn or so. If you turn and turn and it takes time/delay to effect a change or little happens, you likely have a restriction or a leak in the system anywhere from the spray bar to the muffler fitting.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

These engines also came with a "set ring" collar that has a stop to keep the needle in a pre-set range. On several engines I helped with, I found they were too lean inside of the stop, I've needed to move the collar or just get rid of the pin. The small roll pin on the side of the needle's thimble pulls out easily. You must retain the spring clip to keep the needle's setting from moving.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

I'll give that a try. replacing the tubing is easy so that seems like a no brainer. I plan to take the carb off today so i'll take a look at the oring on that thing. Thanks!

RE: Evolution PTS at Altitude - Issues, Please Help!
 

I did, several times. Such measures have no impact on the engine's performance. Sometimes it gets up to full throttle and then dies and sometimes it doesn't even get past half throttle and dies.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Yeah, i'm also going to take the muffler off and replace the gasket. It didn't look properly set so why not try that too i suppose. So much work for a fairly new engine is frustrating.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

I tried going well past the stop but to no avail.

RE: Evolution PTS at Altitude - Issues, Please Help!
 

Thanks to everyone for the suggestions. I really appreciate it! I'm going to try a few things tonight but so far, it doesn't seem to be a blockage or an airleak in the crankcase. I'll keep troubleshooting. Thanks!