Throttle Set-up on my 701 with a 912 Rotax

greetings...I'm new to the site so not sure if this is posted in the most appropriate spot....


i just installed a new Rotax 912 on my 1995 701. i had a Rotax mechanic do the install for me so it was done right. he commented on my throttle cable set up and thought it should be giving me some syncing problems. i was looking for other opinions on this and what others may have done.


the throttle cables are attached to the lever on the passenger side of the firewall. with this set up one cable is about 1' long to the closest carb while the other cable is about 2' long to the other carb. the mechanic felt this difference in cable lengths was giving me some trouble.


has anyone had troubles with this or have any suggestions?





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Comment by Martin Bima on March 25, 2014 at 11:05pm

i also had one short cable and one long one. running rougher and rougher, especially when closing the throttle. i am installing equal lengths now and will do anothee balance.

Comment by Mark Blake on October 2, 2013 at 8:36pm

thanks for the feedback everyone. yes, I've enjoyed my 701...I had it on floats when I first bought it but now i've switched to wheels. I now use it for flight training as I've started an ultralight school here in my neck of the woods.

i'll look into the vernier system a little more to see if it suits my needs. as a trainer i'd want to keep a duel throttle set up in the cockpit.


Comment by Jonathan Porter on September 29, 2013 at 2:09am

We have many hundreds of hours on the 912 with the standard Zenith install.  If installed correctly using the magic replacement parts from Zenith for holding the ends of the sheath.    (we use them on all of our Rotax carbs now - and they remove the 'jumped sleeve' condition).  At first I was sceptical at the different lengths - but our Zenith friends have tested it, and I trusted them - as is usual with the team in Missouri, that trust was well placed - provided the installation is carried out correctly!  Fly safely and remember that carb-balancing is no big deal - and the extra responsiveness from the twin carbs is worth the extra 20 minutes every 100hours or so!

Comment by Chris Aysen on September 26, 2013 at 3:59pm

If the throttle cable works everytime you probably won't have a problem. However, and I experienced this personally, the longer the exposed cable (absence of throttle shield between carb and mechanical throttle arm) the greater the chance friction will cause the cable to bend. This would more often be found when opening the throttle (applying power) then closing it. Once on a takeoff I applied power and before I could realize my rpms were not where they should be the plane was off the ground, yes it happen that quick. I also realized that the plane was climbing just under 800 ft. per. I contiuned the takeoff and stayed in the pattern and landed. When testing on the ground I found the cable on the right carb would bend instead of opening the carb. So essentially I tookoff and landed on one carb. Not that big of deal but it happened. Rpm got to the 4500 area when the plane left the ground. Most setups for the Rotax or on a push/pull arm that runs accross the top of the firewall to each carb. I found if I work and keep lubricated the inside of the throttle shield everything works fine. I've never had the problem since. Consequently, if this has happen to you several times you may want to change the cable(s). Like any other metal; cables can get fatigue if bent to many times.

Comment by Joe Harrington on September 25, 2013 at 11:36pm

Oh, and BTW, it probably would be a little bit better to make this post under "discussions" (in CH 701) rather than a "blog" entry. No biggie though. How are you liking the 912 so far?

Comment by Joe Harrington on September 25, 2013 at 11:32pm

Macfarlane Aviation Products make a great vernier-assist throttle cable control set up for Rotax dual carbs. They work beautifully. It is both a vernier and friction lock combination system that is the best of both worlds (type).;

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