Quote Originally Posted by ...[COLOR=#000000
I found them on MacFarlane's. What is the difference between these and is there any advantage for one over the other?
Fred[/COLOR]
I think the torsion spring from Van’s may be less vulnerable to breakage from vibration for one thing, but that’s just a guess.

I couldn’t stand the original springs and considered them a PITA, if not dangerous... at least with the original conventional friction throttle control that came with my kit. I had a vernier throttle on my previous airplane and loved it, but I have a few friends who were military pilots and they all strongly preferred friction lock throttles, so I decided to keep what I had and get used to it. I tried the McFarlane springs and then the Van’s ones. Then, when getting some training with Paul at Stick & Rudder, he showed me that the springs had been removed from the carbs on his 914 powered bird that we were flying. It worked just fine. Then I discovered that at least 2 of the Kitfoxes at my airport had no springs... one that was approaching 2400 hours on a 1200 hour 80 hp 912. I removed the springs and carefully tested the balance throughout the range. It was good. I believe that the primary reason for the springs is to keep tension on the cables, as mentioned by others. Depending on the cable stiffness, the way they are run, etc., springs may not be needed to maintain carb balance. I have the dual cable from McFarland as I believe most do now. The idea that the throttles go full if a cable breaks also doesn’t appeal to me. When was the last time you heard of a throttle cable breaking? And what if just one breaks or comes loose? Could you figure out in time what’s happening and shove the throttle full to balance the severely vibrating engine, or would you pull it off and probably make it worse? Just wanted to share my thoughts... I am NOT suggesting anyone else do what I did.