Mcfarlane throttle

[Av8r3400]

Can you expand on the Vans torsion spring?

[jrevens]

Can you expand on the Vans torsion spring?

I think it's a spring that circles around the end of the throttle shaft and "winds up" when the throttle is retarded.

[Av8r3400]

I think it's a spring that circles around the end of the throttle shaft and "winds up" when the throttle is retarded.

Does anyone have a source or web-link for these?

[Guy Buchanan]

I ran out to the airport to get some pictures of my throttle system and what did I find? NO AIRPLANE! Dang.

So I dug up some pictures from the build. It's a short rigid cable vernier push/pull throttle cable going through the firewall to a bellcrank that goes from the cable to the carbs on both sides. The bellcrank supports come off the cylinder head water exit on each side. Each end of the bellcrank is supported by a small sealed bearing. The connections from bellcrank to carb are a combination of threaded female rod and two rod ends. That's so I can adjust each strut's length. The idea was that once sync'd, nothing would move and the carbs would remain sync's forever. (Theoretically, of course.)

[mr bill]

Details of the torsional spring install on the carburetor can be seen in Vans service bulletin 18-03-06.

[Av8r3400]

Here's a link to the Vans SB. Link

Now for the $68 question, will VANs sell these springs to the general public or do you need an RV-12 serial number to get them?

[GuppyWN]

Kitfox has a lighter spring. I put them on a couple days ago and it is MUCH better. Still have to crank a little friction on the throttle but 1,000,000 times better.

I’ll try this setup for a bit before deciding on the McFarlane throttle or just removing the springs altogether.

[jiott]

I'm pretty sure Van's will sell to a non-RV builder. Since they are here near me, I have bought quite a bit of stuff from them during my build.

[colospace]

My McFarlane throttle came with a set of lighter springs. Does the Vans Service Bulletin imply an issue with the McFarlane supplied springs?