Evolution .36CL defective

I ran this new motor on the bench for about 2 minutes, it had a bad viberation so i pinch of the fuel to check the prop, and found that it binds up at the top of the stroke, and not just
a little bind, i took the plug out and could not turn it over with out the prop on it. I used brodak 11.5 11.5 fuel so i'm sure i didn't caused it. I got it with the PT-19 from horizon hobbys and i sure hope i dont have a problem getting it replaced.

Any thoughts on this?

Shawn

What it is, is what it is, unless it isn't !!!!!

Shawn,
The Evolution 36 is an ABC engine which means it has an Aluminum piston with Brass sleeve that is Chrome plated. These motors are designed to bind at the top of the stroke. It is a common modern technology in 2 stroke engine design. When you run the motor it will heat up and the sleeve will expand enough to remove alot of the bind, but when it cools it will return. It's not a good idea to turn the motor over when it's cold unless you are starting it. The fact that it binds means you got a good one. As far as the vibration goes it should run smooth with minimal vibration unless you have an out of balance prop.
Greg L. Bahrman

Unless you are running way too rich, not very likely just a thought.

Walter

Put the engine back on the test stand. The fuel you are using is ok. Greg is correct, do not turn the engine over unless you are starting it. Use a 9x5 prop on it.

Back the needle out about 3.5 to 4 turns to get it running. As soon as you have it running adjust the needle for a crackly two stroke, about between a two and four stroke. These engines need low load and fast rpm's to break in properly. Occaisonally pinch the fuel line and let it rev quickly then release back to the needle setting. Run at least ten four ounce tanks thru it, more would be better. Let it cool down so it is just warm to the touch between runs. Check all the bolts for tightness after the first run. It will take about one hour and then you should be good to go.

If you decide you want to shorten the breakin period, that's ok, but be ready to shorten the engine life which means you might as well buy another motor and start over. Don't mean to sound harsh but you do need to break these engines in like I said. It does work. RJ

I dont think i explained this right, it feels like there's a flat spot on the con rod, not a compression bind, i cant even get it to stay running.
Shawn

What it is, is what it is, unless it isn't !!!!!!

Shawn,
You have received some good advice. Mine was much like yours until it had some run time on it. The tightness at the top of the stroke is not due to compression, but to piston fit at the top which is typical of ABC engines.

Bob (rjalphadog) is right about how to "break-in" these engines, small prop at high rpm. The old rule about running them rich was for a different type of engine. One key for the EVO seems to be to run the initial runs without the muffler.
Steve

Just sitting here reading and it kind of seems that what is saying has been lost. I believe he is saying he can no longer turn the motor over even if he wanted to continue to break it in. If it won't turn over it can't be started either which makes it kind of hard to break it in, at least I think this is what he is saying. I've run similar motors and while tight at the top I could turn it over.

I am curious. Was the prop balanced? Is the hole in the prop perhaps too large? Bent crank maybe?

What color is the oil that came out when it was running? Any signs of metal? How tight was it the first time you cranked it and was this the only time?

It could be that it is simply fitted too tight. Mine only had a slight bind at the top.

I can still turn it over, but it wont stay running, the props were balanced and the last one was a 10-6. When i first put it on the bench it turned over and was tight at the top of the stroke, but smooth , it ran for about 2 minutes- no muffler - and i let it cool down, when i tried to restart it it had this flat spot feeling, and it wont stay running. you know when you prime it and the needle valve is closed it will lean out and rev up, well it wont even do that.

Shawn

What it is, is what it is, unless it isn't !!!!!!

Shawn, two thoughts...

What is your home altitude? That can have unexpected impact on engine performance...

Second - are you handy enough to recheck the "torquing" of the head bolts? If you have a bit of engine experience, this may possibly help. If not, do you have a buddy who has messed with engines for several years?

With ALL engines I acquire, I recheck the as-manufactured tightening of the heads. Some factories are worse than others, and some are really good about this. I've found it worthwhile over many years to recheck...

An improperly "torqued" head can distort the head, possibly also the crankcase, enough to cause problems. To check, I "back off" the head bolts a bit, initially about a quarter turn, then - to make sure - another quarter turn (total one half turn). This is sequenced so that the bolts don't 'relax' all on one side, first.

Consider: The EVO 36 has a six-bolt head, with one bolt dead forward toward the prop, right? Call that bolt 12 o'clock. When loosening the bolts that firtst quarter turn, start with that 12 o'clock baby, then go to the "4 o'clock" bolt, then the "8 o'clock."

Cross the head through the glowplug, and next loosen the "2 o'clock," then the "6 o'clock," then the "10 o'clock." The first loosening all six bolts about a quarter turn, done in this sequence, leaves you at the "10 o'clock" bolt; again cross through the glow plug and loosen the "4 o'clock" bolt the next quarter turn, and in the same sequence, give them all that extra to a full half turn from where they were, stock NIB.

Check how free the shaft is around the bottom of the stroke up to where you feel compression. Remember that "feel." Back to the head bolts. In the same kind of sequence, draw the bolts in a slight bit, until you feel some resistance. then back out just enough that the head still feels loose on its seat. After this pass, the head should feel firmly, and squarely, seated.

Repeat around the head in that "skip-a-bolt, then cross to the opposite" sequence. Each time you've put a hair of turn on all six, check to make sure you haven't torqued in a bind. (If you have, back them all off a bit and start again.)

You (almost guaranteed!) will be able to get the head on - securely, and without causing a bind - in less time than it takes to read this. On a few other forums, I'm amazed that otherwise capable model fliers don't realize that mass production factories can't spare the time, or perhaps afford the employees, who have the "feel" to do this right. Some have spent hundreds of dollars on big RC engines, then whined that the factory didn't tighten the head down properly.

Well, duhh, when you buy a car, don't you make sure there's gas in the tank before you go over the mountain and through the woods to Grandmother's house? Or, if not, is it your first reaction that the car company screwed up, and screwed you, by not filling the tank?

WE operate our engines. We owe ourselves (and the poor engines) a little respect. The idea that we learn a little bit by doing such (WARNING: Military gobbledygook follows :- ) 'preventive maintenance' is just another little pleasant plus to our enjoyment of the hobby...

A tight pinch through top dead center is most often a good sign for an engine like the EVO. I hope the problem soon clears away for you.

> i took the plug out and could not turn it over
>with out the prop on it.
This sounds about normal to me.

I had a similar problem with a Brodak 40. If the piston is too tight at the top of the cylinder the engine will be hard to start and will not give of its best. after a season of competition use my tight B40 had a completely knackered conrod and a very worn main bearing but the piston was still tight in the bore. When I rebuilt the engine I lapped to piston to a more sensible fit and that engine is now performing very well - much better than it did when it was too tight.
http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=190149
http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=190831

I have a second one that had only a slight pinch at TDC and that one is a dream to use.

Mike, good point!

Lapping and ABC/AAC/ABN engine to the "right pinch" is a matter of touch and experience, though. Shawn may do better going to the factory to get that "proper" slight pinch at TDC that works for most of the EVOs.
(edit - spelling)

Maybe I can help abit. The last week or two I've been getting the first runs on my Evo36.

The fit at top-dead-center is VERY tight. After 15 or so runs, its still tight. I can flip it easy enough, but to bump it over for prime it feels like its catching on something and offering alot of resistance.

First bunch of runs had the engine quitting very abruptly and multiple times on the same tank of fuel.

I did a bunch of reading here and on 2 other forums....

The consensus was, that the plug that comes with the motor is too cold. I put in an OS#8 .... and the abrupt quitting is gone.

Another consensus was to use regular fuel. What I mean is no additives, which is exactly what I was doing .... bumping the oil content up to 23% with castor. Too much oil in this engine is wisking too much heat away and not allowing the piston to break into the sleeve. This is probably why I still have such a tight fit at TDC. Out of all the runs, maybe 2 were in a wet 2-stroke. The rest are all 4-stroking .... which would not allow the motor to come up to the temp it needs to breakin.

The first 5 bench runs I used the medium venturi, stock exhaust and a 10x6. The next 10+ runs were in the air with 11x4, 4.5, and 5 trying to get the speed in check. The last few runs I've had a problem with surging in flight, and after checking all bolts and switching the tank ... I believe the problem to be a leaking remote needle valve. Last night, I drilled out the LARGE venturi and installed the OS spraybar/needle assembly. (Can buy it at Tower) Haven't had a chance to fly it yet, but I'm optimistic.

At this point I'm not concerned about the tightness of my piston/sleeve. I believe my mistake is running too much oil, and my next flights are going to be out-of-the-jug fuel, which is supposed to be 18% syn/castor.

If the motor blows up .... well, Horizon will get a box of broken parts in it for R&D to look at. I dont think so tho .... I've had several motors just as tight, and once it is broke-in ... they have been great runners. A recent Tower75 comes to mind. Terrible to try to start cause it was so tight. Once it was broke in after a couple gallons of fuel, it was my best running engine.

Change out that plug and try the medium venturi.

Hope this helps .... sorry for the length.

FlySafe! Larry (Larrys4227)

I have only experienced this pinching on my more expensive engines. That this relatively inexpensive engine exhibits this is an indication of its quality. Mine did "lock up" at first. When it would do this I would not try to flip or turn it but would start it by a "back slap", or "bump" start. If you are unfamilier with this technique it has been described previously on this and another forum.

I also went to a hotter plug initially and used standard fuel, not my castor enriched 22% GMA. They do run cool. Smallest venturi, stock needle valve, went to an 11x4 prop, even for run-in. Made it easier to start and didn't load the engine excessively at all. The vibration will lessen, they actually are very smooth when broken in. Good luck, they are good engines once you understand them.

I have followed the following advice on several of my newest ABC, AAC engines and have had very good results.

Use the fuel mix recommended by the manufacturer, added oil WILL cause problems. Chose a prop that runs the engine at the rpm you expect to fly. On my 15s and 25s I use a 7-4 APC, 36-46 an 8-4 cut down from a 10-4. The low pitch will allow the engine to rev freely. Start and run for 30 seconds. Don't run too lean however. Let the engine cool for 5 minutes. Repeat for a total of 20-30 minutes of run time. The engine should require leaning after the first few runs to maintain rpm as the fit establishes. Everything should be fit right by then.

ABC/AAC engines need to break in at the temperature they expect to be run. Running slow or with too much oil will just wear the engine out prematurely and can cause rod damage. The rod damage occurs becuase the cylinder and head do not get hot enough and the resulting piston clearance is too tight, beating the rod out beacause of the pinch at top dead center.

don Burke
Menifee, CA
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways - body thoroughly used up, totally worn out and screaming, WOO HOO, What a Ride!

>The consensus was, that the plug that comes with the motor is
>too cold. I put in an OS#8 .... and the abrupt quitting is
>gone.
>
I had to replace the plug on mine too. It ran too cold and would quit without warning. The removed plug works fine in other engines.

Send it back and get a new one. Bad vibration with a balanced prop shouldn't be. That's what warranties are all about. If you tear into the motor the warranty becomes void.

Meaning no disrespect to all the other statements of advice, the suggestion to send the engine back whence it came, under warrantee, seems to me to be the best of the group of comments. Break-in is not a substitute for incorrect assembly clearances.

R/C folks have also, while breaking in new ABC engines, in addition to NOT babying them with wet, slow, runs, give the cylinder a good dose of heat-gun persuasion before trying to start a new engine. As mentioned above, too much drag will just wear out the connecting rod and piston pin bosses, not break in an engine. Applying a heat gun gets the initial starting clearance loose enough to help avoid killing the connecting rod.

Peter Havriluk

I came across a similar problem once with an OS 40LA that I was asked to run in. Sometimes it would be quite free to flick over TDC then would suddenly lock up and need huge force to free it. I managed to start it several times while it was free but the symptom persisted when trying for another start. Obviously there was something quite wrong so I gave the owner two options, one was that I'd dismantle it to try to find the problem or he could send it back under warranty. He (probably wisely ) chose to send it back. The engine came back about a week later with a note saying they'd run it on the bench with no problem. However when I put a prop on it and flicked it over it felt like an entirely different engine. My guess is they changed the piston/liner and didn't want to admit it had been defective. This was back in the hey-day of peeling liners where OS wouldn't admit to any problem but would fit a new piston/liner to keep the customer "happy".

If it was a 40 LA I would send it back as well, but it's not.

I was going to reply to this post earlier but was looking for the reference I had seen. Here it is:

http://www.rcuniverse.com/forum/m_1850473/anchors_1850473/mpage_1/key_/anchor/tm.htm#1850473

ABC engines are different than ring or other no-ring engines and it is easy to do a lot of damage if your not familiar with them. Hope this helps.

Paul

Sounds to me like there was some loose junk in the engine that has now become part of the engine...send it back.

George