I just had my first broken engine today. Just flying along and my new SK .91 broke a rod, maybe a crank? I haven't opened it up to look yet.
I just had my first oil problem today too, must have been my day for firsts. After I landed my plane I went over to the other pattern plane I took out but I couldn't get it to run?? A YS 1.20FZ. No fuel getting to the carb at all but plenty of pressure? It would run on a prime but as soon as that burnt off it would just quit?
When I got home I pulled the engine and opened up the regulator and diaphragm, all was well. I used my pressure bulb full of fuel and hooked it up to the carb line, couldn't get fuel to flow? Pulled the needle valve and gave the bulb a good squeeze, nasty old oil started flowing out!! Trickling is a better word for it. As soon as the oil was pushed out the fuel started flowing like it should.
This brings up the TO ADD OR NOT TO ADD OIL QUESTION. This also brings up some other points. I have been adding two ounces of Klotz oil to my fuel. Klotz is a blended oil with 20% of the blend being Castor. The reason I have been adding oil is I didn't trust the claim of it being 18% oil, I was thinking it was only 15%, maybe I was wrong??
This was also another MY BAD thing. I usually run my engines dry after a day of flying. In this case I had broken a header on this engine three weeks ago so I put it away wet. It has been pretty cold in Vegas the last few weeks so the oil in the fuel congealed and acted as a plug in the needle valve seat, it's a very small hole. After a good cleaning of all parts the carb is carbing again.
No real point to this ramble but I did want to point out there can be problems by adding oil to your fuel. In my case nothing bad happened but I'm now thinking I should maybe believe the add about the oil content that the hobby shop put out. The add stated 18% oil but it wasn't stated on the can and the can looked just like the Wild Cat fuel that is only 15% oil.
That dumbass married to my wife did it again!!

GB one of our locals tried a new SK 1.08 about two years ago During the first runs the connecting rod and or the rod journal broke. The airplane never got to fly and the gentleman doing the brake in was no beginer and a well versed engine man.

I cannot give you the exact specs but the engine was immediately returned and it was replaced without question. The problem was the replacement engine did the exact same thing. It was a complete writeoff and he just threw it away.

John

I have had a couple of the .91s and had great luck with them. I do have one that I tried to plant on it's nose that still runs but it over heats in about 15 seconds. Before the crash it was perfect. I wasn't over reving either, just doing a turn around and rolling on the throttle. I had it set at 9200 on the ground so even if I was on it the engine shouldn't have broken. I'm going to phone Kangke Monday and tell him about it and make sure opening it up doesn't destroy my waerinty.
I was more surprised about the oil clog I had. I have seen one YS do something like that years ago but it took a lot longer to clog. Maybe it doesn't like the Klotz?? It was sure thick!!
I will let you know if I find out if SK is having a rod problem or not. Sounds like something may be going on.
Gene

Gene, is it the same oil and fuel that you have been mixing all along? The reason I ask is that mixing two oils together can sometimes lead to a gummy mess. When I was repairing IBM card machines, we were very carefull to use the "right" oil. Sintered bronze was the worst as it is usually oil impregnated when new and a couple drops of the wrong oil on it and things would turn nasty.

You need to come out and visit where things are warm. We've had a great couple weeks and it looks like it's going to continue. To nice actually, my pulm trees are in blossom. That shouldn't happen for another 6 weeks or so. Iwas out to the field yesterday with my Sagatia 900. We seem to be going into a thermal soaring phase at the field. One of our new guys is a very experrienced glider pilot. He went nuts over the thermals we were getting. He claimed it was the best day he ever saw. Me, well after about 10 minuts total stick time and never launched or landed, it was just another day. In fact I wish I had my Twist 150 out there. Maybe monday.

Don

Very weird. I know this is off topic but that is odd. Mine still show no signs of wanting to bloom.
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Don, it's the same oil, mater of fact the same bottle. I'm not one of the tune for smoke people, I tune the engine and if it has a smoke trail fine, if not fine. It's usually the oil type used in the fuel giving you the smoke trail anyway and I did change fuels. When Power Master was no longer sold here I went to Wild Cat 15% nitro and it only had 15% oil so I started adding the Klotz, two ounces to the gallon. My engines loved it, just seemed to run smoother? No change in the tune at all. I bought the fuel now sold under the Hobby People brand name, the label looks just like the Wild Cat but HP advertised it as 18% oil but it isn't stated on the label and I didn't trust it so I still added the Klotz. This engine is always hard to get fuel to feed first fire up of the day. Maybe I forgot to clean the needle valve assembly when I went through it? Anyway, I broke the header off at the head a couple weeks ago and I didn't run the engine dry, just hung it up wet. You may be onto something though. This Hobby People fuel may have a different oil blend and the Klotz may make the blend of oil thicken up? I will quit adding oil but then I loose that nice smoke trail!! I will hear all about it again, I fly with a few smoke trail tuners!!
71 and a short sleeve shirt isn't a bad day at all. It was the broken engine and the non starting engine that put a damper on my day. I only took the two planes with me.[&o]
Gene

I think this is a very good topic. I'm one of those who hate spending alot of money on things that fail. I can understand your frustration and throwing out the darn engine because I've done thing similar in the past. Knowing what I know now I think you should pull the engine out of the trash, send it back and call them up and explain what keeps happening. I'd be nice but persistent about it and demand that they fix the problem or get your money back and buy a engine that is a little more reliable. JMHO


I got a question for you guys. Is it possible to cause that kind of damage, if I were to swing a prop out side of the engine manufacture recommendations, as I was braking the motor in?


Pete

I never tossed out an engine. Kangke is very good at standing behind what they sell. I will be calling and getting some information from the owner monday. This engine is under warenty. Even when I kill an engine in a crash there are a lot of screws and parts I use when I'm rebuilding other engines people give me.
I have seen several engines break when I was pitting for a race tems. The cause is simple. An engine has a working RPM range and sometimes the manufacture tends to go a bit too high with the RPMs. They tend to run very small props with different pitches to get those high RPMs then post them. Doesn't always work in the real world. Racers tend to go for as many RPMs they can get and use small props with a high pitch and to get every rev they can get so rods and cranks let go quite often.
In my case I was just flying the basic pattern and pulling a lot less RPMs then the engine calls for so it was a shock to me. The SKs are a low RPM high torque engine anyway and not used for any type of racing.
There could also be a problem in the manufacture. My other SK engines were all great, maybe they are being made in a different plant? I will find out tomorrow. It's not a big deal at the moment, it was just a first for me. A few weeks before I had my first mid air, I seem to be going through a first time faze or something?
I also don't run two strokes very often any longer so i go the cheap route. These engines are great and only $100.00 with a muffler. If there is a problem I will just use another four stroke or spend the money and get another OS two stroke. I have just had great luck with the SKs and like them better then the OS. Some may say you get what you pay for and I'm one of them. I tried SK and like them, if they are having a problem I won't bother with them anymore.
I'm also one of the suckers that bought the MDS line some years back. There was total junk!!!

Oh, I didn't know that. Thanks for the good info.


Pete

Day one of phoning Kangke/Superkraft was a waste. I had problems getting in touch with them when I ordered the SK engine. I question if Kangke is still a full time operation shop these days. I start calling at 9:00 and phone every hour.

GB,

2 ounces added to a new gallon of fuel shouldn't hurt a thing even if the new gallon was 18% oil. I don't thing you have an "oil problem" at all. If you use a pressure tap off the exhaust and don't place an inline filter between the clunk and the needle valve you run the risk of contaminates from the running engine finding their way into the needle valve and carb. You know when you first break-in an engine they often put out a bunch of trash initially. I'd be more suspicious of that than I would the oil.

Regards,

Clay

Clay, the engine with the oil pulgging problem was a YS 1.20 four stroke. Nothing new about a YS 1.20. I think Don is onto something about the oils not mixing well with each other. Oil getting to a solid gummy state in a few weeks isn't normal. I only brought it up because there have been a lot of posts asking about adding oil to the fuel. I usually don't.
I was able to get hold of someone at Kangke. They gave me the number of the service center. Seems there is no one home there either!! I did pull the back plate off the SK and took a look. The big end pin on the crank had broken off, looks like it was sheared pretty clean and flush with the crank.

This is identical damage to what happened to the local I spoke of in post #2 both the first new 1.08 and the replacement 1.08 that was sent.

John

John, I went into the glow engine forum and noticed this has been happening. My other SKs were fine. Two days of phoning and no one to answer a phone?? I got hold of one fellow at one of there outlets and he refered me to there service department. Been calling all day without any luck. I will take the replacement but Kangke is another place I will no longer order from or refer to. If they can't staff an office or pick up the phone then I can't be bothered with them either. My wasted time is worth as much as there time is.

No expert here but a finely sheared crank journal seems indicative of a metalurgical design problem.

The engines I examined were about three years ago and the operator customer is knowledgeable.

I have reached a point in life where anything that costs me lost flying time or wasted trips to the field is totally unacceptable. Its at that point that cheap engines become very costly indeed and I won,t go there.

I don,t care how much harrasment I get at times over spending my money on quality engines. Quality that I know is there simply because I have seen over the years as you that those engines deliver.

John

I agree with you 100% John but I don't use two strokes often enough to pay the price for the OS engines. I have been very happy with the SKs up to this time. First time I have tried to use the Kangke service too, it really sucks!!

That's definitely a manufacturing fault. I'd been wondering if they used a press in crankpin but that one seems to be machined as part of the crankshaft. The usual cause for a break like that is too small a radius where the crankpin blends in with the crankshaft giving a stress riser or overhardening making the pin brittle. Or a combination of the two .

In real life it looks like a press fit?? Doesn't mater what or why, it's just broken. Not being able to get hold of anyone at Kangke is the only real pissmeoff.