king kong 670

[Bmark]

anyone out there running one of these engines, thinking about buying one an would like to know the, good bad an the ugly, before i part with my money. will be putting it on a kitfox 2 an adding floats. been searching an reading a lot about this engine an would like your input on it. thank you all for your time.

[t j]

I have a 670 in my 1996 Ski Doo. That thing still pulls like a freight train!

A big difference between snowmobile Rotaxes and Aircraft Rotaxes is the aircraft versions of the 503 and 583 are de tuned for reliance and longevity.

The clutch in the Ski Doo is set to hold 7200 rpm at full throttle to get the power and torque. I have never been able to hang on to it for more than about 1 or 2 minutes at that speed and only on a hill climb in deep snow. On flat hard snow only about 30 seconds. So...it never sees much time at that rpm.

I figure that if it was in my kitfox it would need to run much less cruise rpm or would have a very short life.

I would love to have that power in my airplane but am waiting to see one in person and talk with someone that has a few hundred hours flying one.

[Bmark]

thank you for the info, i am sure there are some people out there running the 670, but thy may not be a member of this forum. going to try one out on my fox will let you know how it goes. i am sure it will be fun trying to get it dialed in. thanks again for your response.

[t j]

If you put a 670 on a good and light kitfox on floats the only thing that will beat it off the water is the ducks.

[KevinM]

Richard Craig in Alabama has one on his CH701, I think he is in love with it. He has a 3.47 e-box and I think its an Ivo 3 blade medium with static set to 6350. Anyway cruise @ 5600 rpm and 82 mph. 75ft no wind TOs ( him and 10 gal fuel) ,1500fpm climbs and no problems. 5.5GPH ave. with his flying style! Not sure of the hours but more then 20-30 just based on our conversations. And for comparison the 82mph is pretty much top speed for a 701 with a 582. It sounds like he practices STOL ops a LOT so that fuel burn may be higher then ave. Though he should be producing around 66 or so hp at 5600rpm and 701 are draggy buggers so....

My 701 will have a 670 from Rick on it, when its finished....I'm sold. There is some discussion over at the Rotary wings forum about Rick. And my conversions with him left me feeling, like he knew what he was doing. Only have come across one bad thing about his engines and that guy bought a 670, just put his 582 pipe on it and ran it wide out from the get go..... you get what you deserve I guess.

Hope it helps

Kevin

[Bmark]

Thank you for the info Mr. Kevin, went an picked me one up today going to get started on putting it in. hope it runs like your friends Mr. Craig an trouble free that sure would be great. thanks again for input really appreciate it.

[KevinM]

If you are going to build it your self, or if someone else built it, contact Rick I think he will give you details. He really want the 670 to be respected even if he didn't build it.

Kevin

[Bmark]

Rick built it for me, he is only about an hours drive from me. nice man loves to talk rotax. thanks for in put.

[Grogen]

Hello everyone,

I built a Model II and put a 670 in it. Twin 38mm mikuni carbs, C box with 3:1 ratio, 72" power fin prop, green sky altitude compensation system, Custom exhaust by CPI racing in Morgan, Utah.

It made a great mountain airplane out of the fox. Plenty of power. I weighed my 582 befor I sold it and the 670 is 14lbs heavier. The engine is producing 98 hp. The engine is capable of much more if the exhaust was tuned a little better. A project for this summer if I find some time. I would definitely do the 670 again. My field elevation is 5,000. I flew it to Oklahoma once and it jumped off the ground at lower elevation. I have had it up to 13,000 and I was still climbing at 500 fpm even that high.

I cruise at 85, rpm is 5,900 to 6,100 at a little less than half throttle. If you push it up in level flight it will Vne the plane in a couple seconds.

Words of advise and wishes.

There are two versions of the 670. The pre 1991 version has the same crank case bolt pattern as the 582. Makes it nice that you can just bolt it on with no mods to the engine mount. Newer models don't have the same bolt pattern. Same engine, different crank case casting.

If I were to do it again I would get mine bored to 740 to get started. They will crank up to 150 hp. You don't have to use all that but it is nice to have if you need it.

A tuned exhaust is important. Tough to fit it under the cowl but it is critical to get the horsepower and efficiency.

I have over 300 hrs on mine, engine inspections look good so I'm going to press. I talked to CPI about rebuilding my engine and he told me he has rebuilt several 582's at 300 hours and it was not necessary. Rotax will recommend it to cover themselves and to sell parts to you and me. Thorough inspections will let you know when it's time to rebuild.

If you want more info give me a call. 801-388-7753

[rdooley79]

Running a 670 on my plane, Check out my thread in the engines section.

http://www.teamkitfox.com/Forums/showthread.php?t=5500

The exhaust has proven to be the biggest challenge. Rotax Rick sells an exhaust for the 618/670 power valve engines that fits o.k. in the kitfox cowl. However I have found that it should be modified further to mount safely. The exhaust as you know on 2 stroke engines is 1/2 of the equation to make power. The Rotax Rick exhaust enables the 670 to produce 90+ hp with a nice flat power curve. Drinks 4ish gph. All my discoveries and thoughts are in my thread. Couple other guys are adding to the thread with their 670 installs. Come on over and post your findings.