Hi all,

 

Does anyone know of anyone who could tell me of someone that has a rotax 670 in a 701?   I would like to know the climb performance.

 

Thanks,

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We got one right on here.  Let me see if I can sort it out.  I made contact with him a while ago.   Here's a video posted here of his airplane.  Notice the very cool airshock suspension.   https://www.youtube.com/watch?v=ydyWihN9NcQ  

Here he is:      Landon Goudreau

For what it's worth, I would consider this route as well   http://www.recpower.com/3702%20-%203%20cylinder%20-%202%20cycle.htm

Hello,

Did you end up going with a rotax 670 in 701?   How is it performing?

I'm considering similar powerplant as well.

Thanks

Hello,

I did install and use a 670 for a period of time.  The climb and performance were ok.  I switched to a 912 ULS and the performance is better yet, and the 912 uses less fuel and the dependability is much better. At least I feel better!  I mainly switched to the 912 for the dependability of the 4 stroke.  Hope this helps.  For me, if I can afford the difference in price, the 912 is much better overall. 

Good luck in your Build!

Brad

Brad, thanks for the reply!

While you had the rotax 670, did you take your plane on long flights?  Any "high altitude" operation? 

What were the biggest problems you encountered with that engine?  I'm planning on a Warp Drive 70" three blade + 3:1 reduction. What propeller and gear ratio did you use?

I've read threads with mixed opinions about 670, but not many that were specifically installed on a ch701.

I would love to get as many details as possible :)

Mikhail

Hi Mikhail,

I will try to give as many details as I can recall for you to make a good decision. 

  • I had Rotax Rick build the engine.  I had a 3:1 gearbox  You may hear mixed reviews on Rick.  My opinion is he is really a Guru on 2 strokes and will do anything to help people as long as  you don't blame him for the bugs that happen on installs that are not his fault.  I really like Rick.  I can't imagine building and engine and shipping it off to someone who claims to know how to install it.  Seems like a lot of risk.  I am glad there are guys like him out there still willing to do it for us.  Oh, the 3:1 gearbox was ok, but a little less gear may have got my RPM's down.  It took off as short as my 912uls almost.  It doesn't pull near as good as the 912.
  • As said above, you will have bugs to work out.  The 670 goes in inverted on the 701.  Not a big deal, but it ahs to be set up to be used this way.  The crank oiling is easy.  The cooling system should be easy, but people mess this up all the time.  I have worked on motors in all types of things for 35 years and I understand cooling systems well. That  being said, I found out that making the cooling system work proper was a trick.  I blew a base gasket the first hour of flying from having the stat stick without a bleed hole.  When I got the cooling system figured out it ran cool from then on.
  • I lost the stator on a flight.  It literally broke.  I have never saw this before or since.  I think that must have been some Karma payback for not tipping a waitress enough some time in my life. Anyway, I got some practice working on the back of the engine.
  • EGT's were not an issue for me.  I moved the needle based on weather. 
  • The upside down engine floods the plugs regularly.  This is kind of a pain.  Mine did it if it sat a few days.  It was fine when I flew it a lot.  I had the fuel shut off and it still did it.
  • I used the same prop as you were looking at.  I used the taper blade.  Since then I have used the square blade.  No difference I can tell.  Great prop and wonderful guy to work with at Warp.
  • I used Zeniths firewall forward engine mount for the 582. Worked good.  Zenith had to build one as they don't use that set up anymore.  Took 3 weeks.  Not to bad.  Roger at Zenith remembers the 582 Zeniths so he was a great help.
  • The exhaust was a pain in the butt to fit in.  Remember you can't cut up the pipe unless you know what you are doing.  You will kill the power. I had made some pipes for motorcycles so I was able to take Rotax Rick's pipe for an Avid and modify it.  It still fit like a saddle on a camel, but it performed well.  You will also need to do some fiberglass work to make the cowling fit. In hindsight maybe I could have had Zenith let me know who made the pipes for their 582's and contacted them.
  • The engine will do good fuel consumption if you can run it at low RPM.  I found flying it at any real speed required around 5500 rpm or more.  At this RPM is sucks fuel at a record pace.  Easily 7-8 GPH.
  • I kept myself within 100 miles of home when I had this motor.   I had to mix fuel, which I did in the wing tanks, and my engine ran 40:1 mix.  100 miles was the farthest I wanted to fly.  A couple hours and it was fuel time.
  • I live at 820 feet.  The highest I remember flying was 6000 feet.  It ran reasonably well.

I should mention I have had a Geo with a raven redrive in a 701 as well.  Really did not like it.  Heavy and poor performance in my experience. My opinion is that the 670 will work fine for scooting around and having fun.  If I was going any real distance on a regular basis I would put in a UL 582 if I wanted a 2 stroke or save up and buy a 912 ULS.  I also just installed a 912 that had the Zipper big bore kits installed.  That is really a fun motor.  It is super smooth and had a large noticeable power increase over even the ULS I had.  The 670 was fun to fly, but took more maintenance and messing with to keep going. 

Hopefully my opinions don't step on anyone's toes.  I dont' usually post to the forums as I don't want to get the feed back if I should create a fuss.  I hope this helps you with your project.  I don't want to discourage you if you want a 670. I did it and it just was not the right combination for me.

Good luck with your project!

Brad

Thanks for this -- I've always wondered about a 670 in a 701 (I have a few parts of one mothballed -- for another day) and wondered what performance might be like on a light, truly stripped, utilitarian 701...

Do you still have the engine mount for the 670 ? Would you like to sell ?

Please allow me to jump in here......Building a 701 an considering the 670 as my engine of choice. 

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