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Thread: K & B .61


  1. #1

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    K & B .61

    Hey guys,
    Wondering if anyone has any feedback on the K&B .61 Twister engine. I fly SPA, and am looking for some lighter yet affordable power. I have three .61sf's, and love them. Would love to look into a Jett Engine, but simply can't afford to go that route. I have been using a Jett tuned muffler on my O.S.'s, and they are really something. In SPA, the lighter the better, and I have had my best success when I build extremely light, contest balsa, etc. I noticed the Twister weighs 14.25 oz., which is really in the ballpark with the Jett and the O.S. 55. The possibility of having 17 or so oz. of weight in my power would be fantastic, and the price is right. That being said, not looking to have a turd on the front of my Curare just because it's light! If you've run a Twister, tell me about the break in, the power, the reliability of the carb, etc.
    Thanks,
    Lindy

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    RE: K & B .61

    RCU name, "Skylane", has been using an OS 55 AX on his pattern plane's, in SPA, flying Expert, or above class. It haul's the mail, you may want to get hold of him, for prop combination's, fuel, etc.

    Crank

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    AllTheGoodNamesAreTaken's Avatar
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    RE: K & B .61

    For whatever reason, the Twister series doesn't have too many fans. The MECOA site specs on the engine give the same bore and stroke as the classic 6550, but recommend a different prop (12-8). I could be ported to swing larger props at lower RPM and people are trying to get high RPM on an 11-6 or 11-7 - who knows.

    The 55AX has lots of fans and some of the numbers being posted are impressive. I was not impressed with mine. I wasn't getting near the RPM as other people were claiming so I sold mine figuring I had a lemon.

    The Evolution .60 is reasonably priced, has good reviews, and is slightly lighter than the 55AX.
    Don\'\'t just stand there, go get some glue!

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    RE: K & B .61

    Lindy,

    I used a 55 AX in SPA Sportsman on my Cutlass with good success. When I moved to Expert flying a 7 lb Compensator I had problems with the Fig M and Top Hat vertical legs. I removed the center baffle from the muffler and used an 11x7 three blade and the performance was significantly better. But everyone else was using an OS 91 four stroke and flying relatively slow but large maneuvers. My ballistic style with the 55 AX put me at a perceived disadvantage. So, I put a four stroke in the nose and added lead to the tail. And now I fly slower and bigger...

    In the end, it depends on the weight of the plane and on the style of presentation you want. For a 61/2 lb plane the 55 AX is fantastic. I am still using one in my Graupner Kwik Fli III - which happens to weigh 61/2 lb.

    Jeff
    Skylane N9214G
    SPA L243 CPA 84

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    RE: K & B .61

    Thanks guys. We have three guys flying the O.S. 55 with a Jett muffler here in the Texas-Oklahoma area SPA. Two in Phoenix 7's and one in a Killer Kaos. I've been very impressed with the engine. My Curare, just before it's final flight, weighed exactly 7lbs with the O.S. .61SF and a Jett tuned muffler. I had been flying it for most of two seasons with an O.S. 61FX, and added the Jett muffler this year. I was turning about 13,300 on the ground with the .61Fx, flying 20% fuel, and a 12x6 apc. My dad mentioned we had two SF's so I decided to bolt one on and see what it would do. I used the same setup and prop, but on the ground was turning about 12,800 to 12,900. However, in the air, the SF just wouldn't quit. With some of my maneuver's the FX would sag, but SF just kept digging, that thing is stout. I know as I read this I'm wondering, "so why are you looking to change?" lol. When I first built the Curare, and before some dings and repairs and weight, etc. it weighed just under 6 1/2 pounds. I salvaged the wing, the horizontal and vertical stab, and plan on building another one this off season. I've been ultra-coating, but want to paint. I also think with a few tweaks and a lighter engine, I could have the same power that was really moving a 7lb plane moving a 6lb plane. That's why I'm investigating engines in that 13 to 14oz. range (without muffler). The .55's with the Jett mufflers are taching 13,100 to 13,300 with a 12x6. That's essentially the same power I had with my FX, only 7 or so ounces lighter. That could be magic. I read through some responses on another post regarding powering a Dirty Birdy, and can't seem to find a lot of good feedback on the K&B, so I will look at the O.S. 55 instead. I had to ask with the K&B at $109.95.

    So I'll ask you guys with the 55's, any idea how it's power compares with the SF? I guess now I'm trying to determine if it's worth it to save the weight going to a .55

    Thanks again for your feedback!

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    RE: K & B .61

    The Jett muffler works best on the OS .55AX when using an 11x6 or lighter, load on the engine. Other wise, the muffler is just being a muffler and is not resonating/adding power to the engine.

    Watch the nitro content of the fuel when using the Jett, or other resonant muffler. It wouldn't be difficult to run into preignition problems on a warm/hot summer day. Of course, your glow plug life will drop when such a thing happens, letting you know that things are getting a bit too hot.


    Ed Cregger
    \"Practice makes prefect\"

    Saito Club Member #52

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    RE: K & B .61

    ORIGINAL: NM2K

    The Jett muffler works best on the OS .55AX when using an 11x6 or lighter, load on the engine. Other wise, the muffler is just being a muffler and is not resonating/adding power to the engine.

    Watch the nitro content of the fuel when using the Jett, or other resonant muffler. It wouldn't be difficult to run into preignition problems on a warm/hot summer day. Of course, your glow plug life will drop when such a thing happens, letting you know that things are getting a bit too hot.


    Ed Cregger

    Gents,

    I do use a temperature warning LED in the canopy, see the pictures, normal temperatures the LED is blinking green, duty cycle depending on temperature level between 150 and 180 degrees Celcius, above 200 degrees β€œRED” and only to reset by switch off the power of the electronic system. So after a flight I do know if the temperature was above that 200 degrees C on any moment.
    I do mix my fuel "on the field" to have the right nitro amount.

    Ask your local electronic engineer because it can safe you a lot of money,

    Cees


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  8. #8
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    RE: K & B .61

    Check out the sister forum at RC groups thread Magnum .61 XLS.

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    RE: K & B .61

    Hi Lindy,
    I have a 61 Twister with the tuned muffler and have it on a Cermark F16 (the old wooden version). I have an APC 11x9 on it and am running Wildcat 15%. I have never tached the engine - really don't care. The reason is that I've had this engine for 8 years and it pulls that plane at 113 mph and has never given me a hint of a problem!! I have over 125 flights on the plane. I love the engine but I'm sure that it is not as strong as the offerings like Rossi, Jett and the myriad of older OS's.

    Great little engine for the price!

    Gene

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    RE: K & B .61

    I have had a K&B Twister on a scratch built Corsair A-7 that is 8.5 pounds and like it just fine. A friend has two of them and we have tached one at 12,600 rpm on 10% nitro with an 11 x 7 APC prop. That was with the ringed silver K&B short muffler and not the longer tuned muffler that came on ours. I understand that now that longer tuned muffler is not sold.

    The picture shows a regular K&B .61, Jett .90, and Twister with tuned muffler on the planes from the bottom up.



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  11. #11

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    RE: K & B .61

    Cjet,

    Love those prop jets!! I didn't realize that they quit making the tuned muffler for the twister 61. Too bad.

    Gene

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    RE: K & B .61

    Hey Gene, do you know how much your F-16 weighs?
    Thanks guys for all the input, very helpful!
    ORIGINAL: Gene Margiotti

    Hi Lindy,
    I have a 61 Twister with the tuned muffler and have it on a Cermark F16 (the old wooden version). I have an APC 11x9 on it and am running Wildcat 15%. I have never tached the engine - really don't care. The reason is that I've had this engine for 8 years and it pulls that plane at 113 mph and has never given me a hint of a problem!! I have over 125 flights on the plane. I love the engine but I'm sure that it is not as strong as the offerings like Rossi, Jett and the myriad of older OS's.

    Great little engine for the price!

    Gene

  13. #13

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    RE: K & B .61

    I have a twister that was built by Clarence Lee. I think he hand fits the engine. I am not sure if there are any porting modifications. I recorded the following with 15% Powermaster blend:

    APC 11x7 with stock muffler with baffle 12,000 rpm
    APC 11x7 with stock muffler w/o baffle12,700 rpm
    APC 11x6 with mac 10cc pipe14,300 rpm
    APC 10x8 with mac 10cc pipe14,700rpm

    I do not have a Jett Stream muffler that fitx this engine. I have flown this engine on a World Intruder, but had to had weight to the front of the plane to balance. This might be a good option if you are needing a light engine. For reference, I am runnig a Rossi 60 long stroke on the Intruder with a JettStram 60-90 that turns an APC 11x7 at 14,300 rpm with spirited performance. Another light engine option is the Evo 60 with the blue Jett Stream. I have one that was on a Phoenix 7 turning APC 11x6 and APC 10x8 both at approximately 15,200 on 15 % Power Master. Good luck with our choice.

    Energyman 1947

    Club Jett #3

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    RE: K & B .61

    I found an old thread with some good info on the K&B 61 as well as the Lee Modified .61

    http://www.rcuniverse.com/forum/m_51..._1/key_/tm.htm

    turbo


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