Tbobflow

Oh man, this is cool as heck.

I just got this engine NIB and I am just amazed. I have always wanted one of these engines and now I have one. I'm going to take a bunch of pictures of it and add them to this thread later. I can't decide whether to run the engine or just hang on to it or what. Part of me really wants to run it. The other part is thinking "how could you run that engine it belongs on display" but hey life is short and you need to fill it with as many super cool things as you can.

Anyway, I'd love to hear from any of you that have run this engine before and what you ran it in, share any pictures of your setups etc.

Thanks, and BOOSTON!

Tbob

dogshome

Watching with interest

Tbobflow

I'm having some trouble with uploading these pictures, bear with me.

Tbobflow

I'll have to do these pictures tomorrow from my PC, sorry. My first observation about the engine is that the carb bore seems so tiny, the barrel has a diameter that is noticeably smaller than the carb body, and it seems awful small for a 2.5hp engine.

Tbobflow

Here is a shot of the carb showing what I described earlier.

Tbobflow

Tbobflow

It is completely satisfying to upload a correctly oriented picture, look at the preview and see it correctly oriented and then post it and see it on its side.

1QwkSport2.5r

Seems to be an iPad/iPhone thing with the sideways photos. It happens to me every so often.

Tbobflow

Agreed, I bet it tags a "up" direction on it somehow that gets confused

Bax

My Feedback: (11)

While the carb venturi opening may look small, it's the correct size and engine runs very well with it. We used to run them with a 13.5 x 13.3 APC propeller, and they would turn them near 10K on the ground.

One thing of note is that the engine would take nearly five gallons worth of running before they would really "come in" and be totally reliable.

Tbobflow

Tbobflow

Tbobflow

Tbobflow

Thanks for the advice Bax. I never doubted that the carb was setup correctly just observing. Yeah, I get you on the 5 gallons, there are a lot of srufaces in the blower that need to seat up and run in.

Tbob

dogshome

I thought you were teasing with the single photo

But then, there we go, a full frontal a few posts later

Tbobflow

oh no, I'm no tease!

Also I noticed that the spec sheet indicates a weight for the engine of 1030g but my scales says more like 1056g, not sure what that plastic bag weighs, but I bet not 26g.

I've been told that these will not make the power that a YS115S will make, but I bet it's still no slouch. Still looking to hear from some people who have run this before!

Tbob

Sandyt

Tbob, I have one, and I spent a considerable amount of time trying to get it to run properly. It was on an old GP Ultra Sport 1000, and while it sounded great and had decent power, I had a lot more dead-stick landings than powered ones . I finally replaced it with an inexpensive OS AX-120, and the US now flies like it should. The SP-120 is a beautiful piece, but as a power plant, I can hardly recommend it. If I were you, I'd mount it on the wall and admire it, rather than run it.

BTW, should you decide to run it, my notes indicate that the midrange was always too rich. This, plus the fact that the supercharger housing allows oil to collect in it, unfortunately causes the engine to quit frequently when you get it inverted during flight. If you run yours, I hope you have better luck than I did. Many years ago, I personally asked Mike McConville about his experiences as he used one in early pattern contests. He told me that while he couldn't remember a lot of specifics, he did recall that the engine was a bear to keep running.

Good Luck!

SandyT

308jockey

I have to disagree with Sandy T, I ran two of these in AMA pattern in the 90's and have another one in a pattern plane of that vintage now. It's by far my favorite engine made, one of the coolest engines ever. I agree with Bax though, it takes some fuel to get it run in. The way we ran them was with a 14x10 or 15x10 APC prop turning around 9500-9800 on the ground with an AAP header and pipe. Never have liked the factory exhaust, the muffler gets hot, expands and falls off every time. Run 20-25% fuels, I always have liked the Cool Power pattern blend. Needle should be open about 3/4 of a turn give or take a click. If you start having to do a lot of adjusting to the needle there is something else wrong. Turn the idle adjustment to full lean and leave it there. This engine does idle a bit rich but rarely gave problems in an inverted engine installation. Use a fuel filter. I always used the OS Type F plug but there may be some others that work. Run the fuel out of it at the end of the day always. This engine will take a 9.5 pound pattern plane and fly the biggest loops you ever saw. You've scored a great powerplant here. If you don't want to keep it let me know.

Rick H.

drac1

My Feedback: (4)

I picked up a NIB one about 12 months ago, but haven't run it. I've heard good and bad about their reliability, but like you I think they are cool and it is a great addition to my collection. I doubt if I'll put it in a model or run it. Just put it on the shelf and look at it.

YS's are the engine of choice these days.

1QwkSport2.5r

I think the OS has the nostalgia factor where the YS is a 'meh' sort of thing. Is it fair to tell the OP 'just put it on the shelf' when it seems pretty clear to me he wants to run it and fly it? And why on earth say 'YS is the engine of choice these days' - what does that have to do with this thread?

Never a dull moment on this forum.

drac1

My Feedback: (4)

If you took the time to read the posts properly, you would know the OP is undecided whether to run it or not.

I did not tell him not to run it, I said that I will most likely not run mine.

As for the YS reference, well again if you read the posts properly, you would know that the OP made a comparison to YS himself. My comments were relevant to this thread.

Never a dull moment? You certainly try to make it that way.

1QwkSport2.5r

I read everything properly. You're right, according to the beginning of the thread, he was undecided. I have a feeling with the right information, the OP will get his to run just fine. I've been in contact with a gentleman that has had great luck with the 120SP and has learned how to avoid the mishaps many seem to have. He is willing to share his experience with the OP here, so perhaps with this information the OP will be more motivated to run his and have success doing so?

The only thing the OP referenced is the 120sp won't make the power of a YS 115. Based on the wording, he has a 120sp and not a 115 YS. So yeah, he referenced YS, but I still don't agree with your comment. But that's okay - we're all entitled to our opinions.

M75771

As to the carb Venturi size, as I understood it was reduced in size at least once, perhaps twice during the production of the engine. I know this to be true as I had the chance to personally inspect a very early version vs a later version. Both engines we owned by a fellow club member and active pattern flyer, Dennis Worley. Additionally, Ray Meyer, the Masters class winner at the 1994 N-PAC told me the centuriescenturies were reduced because of crankcase cracking problems when fuels with 25% or higher nitro were used. Ray used the supercharged OS 1.2 and was a staunch supporter of it. I forget the Venturi size of the early engine, but if I can find a copy of Clarence Lee's review of it in RCM, I'm sure he noted that info. In practice, these engines preferred smaller props than YS 1.2's; they liked to rev. Typical of a mechanically supercharged engine. I rebuilt one of the club member's engine due to a bad brg in the blower. The OS is a powerful engine, but my YS 1.2 AC would dust it in a vertical pull with planes of equal size and weight.

Tbobflow

Thanks for all the great feedback guys. I more great advice that I was even hoping for! Yes I am on the fence as far as running it, but part of me really really wants to run it.

Yes I am also very interested in the YS engines, and having just returned to the hobby after taking several years away i'll admit I am still a little overwhelmed by how much everything has changed since 2006 or so. I recall the YS engines being around, but I don't recall them being regarded as the final solution for big power like they seem to be today.

Back to this 120SP - I KNEW THE VENTURI WAS SIGNIFICANT. You almost never see a "detune" feature like that in a device unless there is a back story! I had a feelign that this OS120SP setup was no where near its max power level as supplied. Cracking cases, now thats where its at! I am interested in learning more about the carb variations over the production run. Wonder if they were all called "C14" carbs regardless of the venturi size?

I have watched a couple of video clips of this engine running on youtube, but I don't hear any kind of noticeable gear drive blower whine from the engines in these video clips.

I have only found one vid clip of the engine flying in a plane and it does dead stick at least once :P

Thanks for all your input!

DISCUS54

My Feedback: (211)

The OS 120SP Surpass was always a smooth runner http://youtu.be/DamXX7DkeBU. and other manufacturers have used OS's ideas with great success.