Last Tuesday I flew my PTS Mustang for the 11th time without a problem, until my motor started acting up. When I lowered my throttle to 50-25% she wouldn't run smooth... rpms were not steady. She seemed to be a little under powered at times. I landed her and the engine quit when I went to taxi it back.

I thought I ran out of fuel, but she still had a 1/4 Glow still in her. The Dew point was over 75% that day... and the temp was 90*+. Do you guys think the Temp and Dew point has a lot to do with how a 2 Stroke Glow will run? I re-started the engine and ran it much richer than I usually do... and it seemed fine after that.

Does weather conditions play a role in our carb adjustments?

[&:]


As soon as I heard the engine not sounding right, I brought her in resulting in preventing a " Dead Stick." [8D]



Luftwaffe Oberst
Radio Aero Modelers Club
Pulaski, NY

My evo ran this way all the time, which is why I got rid of it (and the other two I bought).

Come on now, I had a 11 flights with no problems. If they were that bad they wouldn't be in business. Plus I love how it starts in one flip of the prop. My O.S. 40 never could do that?


Luftwaffe Oberst
Radio Aero Modelers Club
Pulaski, NY

You can think what you want to think. All three gave me the same problems. And they were all looked over by pro's. We tried different fuels, with no avail. On my 100, it was on the Excelleron 90. I had that engine plane combination for about four months trying to get the thing to run long enough to get one complete flight out of the plane, but never could. It would start, but not tranit to full throttle. Then when we thought we had it ok for transit to full, it would not idle back properly without shutting down. When we thought we had it running good for all throttle settings, I would put the plane up in the air only to have it die after three or four orbits.

At first we thought it was fuel, then thought it was something wrong with the fuel line or tank. We swapped out glow plugs. Removed and checked the tank and fuel lines. Then someone suggested a new carb. So, someone brought a new carb in (this carb cost over 80 bucks) and it worked out ok, but that takes away from the reason I bought the EVO to begin with.... cost. If I wanted to pay that much for an engine, I would have bought an OS, which I eventually did.

I put an OS 1.20 AX on that plane, and after break in, and after changing NOTHING on that plane after all I had done previously.. not the fuel line, not the tank, nothing.. it flew just fine and still does. The very first tank after break in was the first time I flew that Excelleron 90 for a full 12 minute flight.

By the way, the 46 did the same thing after I had it running, what I thought was just fine on a different plane. It ran fine for about 5 tanks then it started with the same thing as the 100 did. Then when I tried to run the 60, well, that was a ditto of the 100. They just would not run right. It was extremely frustrating because I would have never figured that all three engines would give me the same problems.

I have a Super Tigre that runs great. Leaks a little fuel from the needle valve guide, but other than that, it runs great. And, I have one OS 40 LA, three OS .46's, one OS 50, one Super Tigre 75, and three OS 1.20's. All start perfectly (as you say, one flip) and run just fine, and are very easy to tune.

Sorry, but no more Evolution engines for me.

DS.

yes wether condition may creat prob in engine.or some durst come in the filter

I would agree with the weather idea if this was a one time thing, but this was every time I tried to run those engines throughout the course of the entire season. I bought the OS 1.20 AX toward the end of the flying season and it was the only thing that saved my season from a total lack of flying and a lot of frustration with the Excelleron 90. Now, thought, it runs and flys just fine.

Like I said, I flew the bird 11x's and no problems. Just the last flight... it was very hot and humid. I could have sucked a black fly in my carb... I'll have to check.



Luftwaffe Oberst
Radio Aero Modelers Club
Pulaski, NY

Luff, I will confirm the weather statement as well. I have an OS .40 LA that I had never had an issue with. The first really hot/humid day I took it out I had a deadstick on my first flight. There happened to be a real good engine guy at my field that day that saw I was having problems (I am a newbie). He came over, fiddled with the High Speed Needle for about 30 seconds before having it running like a top. If I was you I would get one of the more experienced people at your field to check over your engine. By experienced I mean someone that is good with engines. Someone here made the statement that the guy that is good with engines is the guy flying all day without issue, not the guy spending all day fiddling with engines. In my case the guy that helped me was out there flying nothing but twin engine planes so I expect he knew what he was doing (which he obviously did).

Now having said all of that I don't mean to discredit CG's comments. People have different experiences with different equipment. He obviously had bad experiences with Evo engines so obviously he shouldn't buy them. However if you have had good experiences with them by all means continue to use them. Too many times I see people treat their favorite equipment like a religion. Before you give see if you can't get that engine Exorcised

I'm no engine pro by any stretch of the imagination, but I do know that down here in Texas the weather does have some effect on engine performance. With these humid times like now, it usually requires a bit more of a richer setting. Just make sure you tune before take off especially on the first flight of the day. Always lean for max RPM then richen up a couple of clicks back or 300 RPM if you're using a tach. I like evos. I only have one which is their .46 and its run perfect for me. I wouldn't worry too much about it, just get it tuned right.

Good luck.

I have this same engine. Check the seal between the carb and the crankcase. If your still on the glow plug you broke the motor in with, good chance it needs changed.
The engine hates cold weather. Throttle transision has never been good , but the few times it has run , it has had lots of power.
It`s the only 2 stroke I have , so I keep messing with it.

Yes...I'm running the same glow plug. I will replace it. Thanks




Your right... Whew, I guess it is normal. It took a extra 1/4 turn richer... than she ran fine. No one was at the field except for my wife... so I took a guess at the problem. It scared me when she started to sound sick after my second flight that day. But when I landed it and it quit, I started to worry. My last flight I richened it and it was fine... didn't know that was normal in hot humid conditions.

I told my wife I was going to question it that day it happened on this forum because I didn't know.


Thanks guys!


Luftwaffe Oberst
Radio Aero Modelers Club
Pulaski, NY

These Evolution engines like hotter plugs than the OS 8. That is most likely the problem. A hotter plug turned mine into new engines. The Saito SS plug is a very good one for the Evolutions. You will gain much more power and it will run way smoother. I ran an Evo .455 yesterday after a year of not using it. Put a SS plug in it and a Tower's muffler on it for the first time. Wow. The .46NT is a great engine too.

If you have any of the older type of Tower's mufflers, use those as they are even better. The newer ones from Tower seem hotter than the OS 8, but not as hot as the older plugs. The new ones work well if you don't have the Saito SS plugs.

I read some where that someone took out the baffle, do you suggest that? And would it harm my engine if I did that, and would I gain some power? I'll go to my LHS and ask for a hotter glow plug. I have a few new stock replacements... I might try a new one , then go from there.


Luftwaffe Oberst
Radio Aero Modelers Club
Pulaski, NY

Yeah, I thought they ran funny every week. [X(]

In the engine forum, there was a thread about the evo 100 and a change in the throttle spring that caused some problems. He said that he stretched the spring, then found a replacement that had more tension and that fixed his problem.

In another one, the issue of hotter glow plugs came up.

And, yet in another one, someone replaced a carb (as was suggested to me) and that fixed it.. he put an OS carb in its place.

This is the first time (only because I've not read it anywhere else, not that it's not the first time it's been mentioned, just the first time I have heard this fix) that someone mentioned about the o'ring at the carb base. Perhaps that is the fix, I don't know. I removed the mixture restrictors from the needle valve, and made low-speed adjustment galore with no light at the end of the tunnel.

So, I won't belabor this issue, I just lost my faith in the Evo engines and that's that. Hey, if you guys are having great luck with them, then more power to you. I'll stick with the OS's. At least I have confidence in them where I lost it with the Evo's and I feel that I did give them a fair chance.

DS.

I sniped the pin off on the needle valve, because everytime I had to remove the cowel, I had to remove it along with the muffler, prop, harmonic balancer. ( If that's what we call it ) I was tired of pulling on the spring to get the valve out. My low end is not a problem so I left that alone.


Luftwaffe Oberst
Radio Aero Modelers Club
Pulaski, NY

Yes, remove the baffle you will gain 100 rpm's

WOW, a whole 100 RPM. Watch out everyone. Rocket ship comint through.

Seriously, 100 more in that RPM is chicken feed.

Changes in humidity DO effect mixture some. That's why needle valves are adjustable.

Thanks bruce, I'll take the baffle out... it can't do any harm, plus I like a loud plane anyway.


Thank You everyone, for telling me that humidity and temp does effect preformance.



Now I know.


Luftwaffe Oberst
Radio Aero Modelers Club
AMA District II
Pulaski, NY

I wonder how many fields have been lost by loud planes?engine manufactures design mufflers to keep the noise down and with in nouse limits set by the ama and most club fields and for the sake of 100 rpm you make a louder engine .

Temp and humidity do have an effect. How much? Not much with most engines. A couple of clicks of needle worst case unless the engine is a dog.

Atmospheric pressure has as much effect. don't just check two, check all three. Or just adjust the needle first thing.

You've mentioned an important thing and not mentioned another thing. Your engine sounds like a new one with 11 or so flights. That's about the time that low-speed needle tuning comes into play with a bunch of new engines. No mention of anyone thinking about that. And experts who suggest a new carb should have tried to set the lowspeed properly before resorting to that major cure. And truth is, you ought to be able to point to a major problem that is obvious with the carb and that isn't fixable before resorting to a new carb. I've seen a number of Evo's that ran like crap. And a couple of the ones that got their lowneedle tuned didn't run like crap afterward.

A significant number of new engines benefit from lowneedle tuning.

I must have had 20 or so Evolutions on students planes so far. Mostly the .45TPS, but a fair number of the 60 size as well.

I've never had one that didn't run well.

I've had several where the factory set low speed limiter was off so that the low end couldn't be leaned out enough. Takes a few seconds to remove the limter and lean out the low end.

I have a used and abused Evo .45TPS engine on my LT-40 that I bought cheap after an ex-student piled in his trainer and moved to larger planes. I pulled the baffle on that one, and you get considerably more than 100rpm with that mod. I also turn an 11x5 prop, and it will haul my LT-40 almost straight up. With the baffle out, the power is close to the OS .46AX. It does make more noise than with the baffle in, but less noise than most other engines in it's class, that Evo muffler is really quiet. My OS .46AXes with Slimline pits mufflers are much louder than the Evo with the removed baffle.

On the Evo carbs, the low end does affect the high end mixture and vice-versa more than on the OS carbs. This isn't a problem, and it's common on a lot of engines. But if you approach tuning the engine as if the two mixture settings are totally seperate you can get real frustrated.

Lots of people have favorate engines. It's funny reading someone bad-mounthing an engine then swearing that their favorate brand is the best. Look around, and you can find plenty of people who have had problems with that same person's favorate and have sworn off that brand.

IMnsHO, OS makes great carbs, but they use nickle plated liners that wear out faster than the chrome used in many other makes. And the whole plastic backplate and plastic needle valve assembly thing is for the birds. I've seen dozens of plastic needle valves get the fuel nipple sheared off. On a conventional needle, an easy out would pull the nipple, and a new nipple is a few cents. On an OS, you have to replace the whole needle body. And then there was the whole OS .46 liner pealing problem a while back. Seems like they have it fixed though. That said, I own several OS engines, like them, and use them. But they aren't perfect.

Thanks, but after the numerous bad experiences I've had with them, I will stick with OS's.

I've no problem with that.

I do have a problem with you coming in and proclaiming that any engine that isn't your preferred brand is junk when the question wasn' t "what's a good engine" but instead was a simple question about weather changest causing the engine's mixture to change.

By ranting on about the engine, you gave the impression that the change experienced was due to some flaw in the engine, while it was clearly the change in the weather conditions. Even OS engines change mixture settings with weather changes. Your post was less than helpful and totally off the point of the question, which is why I responded as I did.

If you had written that same response to someone asking "what engine should I buy", my response to you would have been different.

OK, after I changed the Glow Plug to a O.S. Glow... It still was acting up. I almost had a "Dead Stick!" When I tried to throttle up, she started to die... I just managed to land without hitting the tall grass at the end of the runway. [X(]


I quickly got the plane back on my work table... and I took out the limiter in the Low end Needle Valve, and leaned it as far as I could with the blue coller still on it. I took out the baffle out of the muffler, and I re-sat the Carb.

I had a used thicker black rubber O-ring, and replaced that cheap thin red stock one... and my engine now runs better than ever. I used the thread locker on the allen screws on the carb... I think the carb loosened up a bit giving me the unsteady RPM's.


I put a Small Engine Tach on my plane and I now have a increase of 168 rpms. Maybe because my carb was raised a mm. My low end was part of the problem as well... it was dumping fuel in my carb if I idled for a minute or so, resulting my engine to sputter if I slamed the throttle forward too quickly.

Now I have a slight hesitation... I can live with that.

Thanks Ken for giving me a direction in what to look for, and Mongo2 for the baffle suggestion... and Insanemoondoggie telling me to re-seat the Carb.[sm=thumbs_up.gif]



Luftwaffe Oberst
Radio Aero Modelers Club
AMA District II
Pulaski, NY