Throttle linkage

[Dick B in KY]

I have just started my phase 1 (Supersport with 912ULS) and am finding that the McFarland dual throttle linkage is trying to bind and stick in place after the friction lock has been tightened and then loosened. Has anyone else had these symptoms and what was your solution? Linkage says not to lubricate at friction nut.

Thanks,
Dick B

[Av8r3400]

Maybe take it apart and clean it thoroughly. I'd use isopropyl alcohol.

[vetdrem]

I recently replaced my throttle system with the macfarland unit, and I love it. Before I laid out the cash, I called the company and asked a few questions regarding their product. they were extremely helpful. I would suggest that you call them directly and ask for their opinion of to remedy the problem. I bet you will be impressed with them.

Louie

[HansLab]

what is a macpharland unit? A picture would surely help...

[vetdrem]

Sorry, what I should have said was "McFarland dual throttle linkage ". I believe that what I installed was the same as the one in question, but the point of my reply was that the company was very customer friendly, I would start my troubleshooting with a call to them.

Louie

[Av8r3400]

what is a macpharland unit? A picture would surely help...

It's the dual cable throttle handle sold by several suppliers.

Link (http://http://www.aircraftspruce.com/catalog/appages/rotaxdualthrottle.php?clickkey=11504)

[Pilot4Life]

I couldn't get that Link to work, so here's one to the manufacturers page...

http://www.mcfarlane-aviation.com/Details.aspx?Article=199

[Dick B in KY]

Contacted the manufacturer, very nice tech rep. Getting a new friction nut packing kit and new springs for the Rotax carbs-not as strong as original so don't have to tighten friction nut as tight. We'll see how this all works out.

Dick B

[Jerrytex]

I took the return springs off of the carbs on my 912. The throttle cables are thick enough to move the carb linkages with no issues. I barely have to use the friction nut. Since there are no springs it stays where you put it with just a little tightening. I think there are several people on here that took them off as well.

[dholly]

I want to change out the old style Vernier in my model 4 w/912 to McFarland's Vernier-Assist Throttle Control. Can someone save me a trip to the hanger and difinitively advise which control length is required? Thanks much.

[cap01]

I would like to change from the crappy cables and springs on my model IV , but I have Lowell's gizmo for syncing carbs . it makes it so easy to sync that I won't give it up

[Dick B in KY]

Just to update the thread, I changed the friction lock fiber washers and installed the less tension springs from McFarland for the Rotax. System works like a charm now, very smooth and I don't have to tighten the friction lock very much to hold throttle position. Problem solved!!!

Dick B

[Pilot4Life]

Great to hear! Nice to have a relatively easy fix...Good Job Dick B.

[Allan]

I took the return springs off of the carbs on my 912. The throttle cables are thick enough to move the carb linkages with no issues. I barely have to use the friction nut. Since there are no springs it stays where you put it with just a little tightening. I think there are several people on here that took them off as well.

I am new to this kitfox4 with a 912ul but I don't like the throttle it goes to full throttle by itself. I have to constantly lock and unlock the throttle or hold it all the time. So you are saying to remove the string on the carb and this will be ok the engine will run smooth and not stall out?

[DesertFox4]

Alan- depends on which throttle cable system you have. There are a couple different cable systems on model 4's. I use the stiffer throttle cable from Kitfox Aircraft. It is strong enough to push the carbs to wide open throttle without help from the springs. I removed both springs.
A photo of yours would help determine if you could do without the springs.

[Allan]

I know there are two Bing 64 Carbs and there are two cables going into the throttle assembly the year was 1996 when it was started and finished in 1998 can't get a picture because the plane is in a hanger. I saw the spring on the carb it's about 1 1/2" long. The cable bolts to the carb and then the ends are connected with a set screw to carb linkage with the spring pulling it down.

[HansLab]

the springs on the carbs tend to be a safety-item: when cables break they will be pulled open (unless you have the sprung-close version - but I can't imagine why that could be) and you could make it to the field with a running engine.....

I too have changed the springs for 'softer' ones: my Vernier-throttle kept moving forward (to the spring, = throttle-up), but now I've done that, the issue is over.

I wouldn't like to fly whithout'm.

Happy Flying!!

[HighWing]

On my second Model IV, I put the softer springs on the carburetors and am having second thoughts about it. About every fourth or fifth landing, the engine will quit as I touch and it doesn't want to start right away which leaves me blocking a runway.

My first Model IV had the strong springs, but I put a counteracting spring between the center arm of the bellcrank and the firewall which took out all the tendency for the throttle to run to full if the knob was bumped. My feeling is that there is some slop in the system due to the softer springs which makes the throttle setting on final not as precise as I would like. I never had the engine quitting problem with my first set-up.

[P Morel]

I have the same set up that Lowell described on his first set up with a counter spring between the bellcrank and firewall with almost neutral tension. Now over 600 hours with no issues. I just wasn't comfortable with the full throttle idea especially on the ground.

[HighWing]

Thanks for the response Paul. It got me on the computer and I ordered new springs from Lockwood and will be converting to the old system when they come. With the original system, I think the stronger springs are necessary with the possibility of play in the two separate cable runs. I also feel that it would be more difficult to sync the carburetors if the spring tension was not strong enough to overcome all friction in the system.

[jiott]

McFarlane has two softer springs for the Rotax 912; somewhat softer (#6534) and a much softer (can't find the part #). I have been using the 6534 for 26 hours now with no problems. It still has enough tension to keep all the slop out of the system, but does not require such high friction to keep it from creeping forward. It will still definitely go to full throttle if the cable breaks.

Jim

[HighWing]

This is in fact, I believe more complex than we might at first think.

With my current Model IV, I used a soft spring during the test phase. I noticed on one thorough check that both springs were broken. I thought that a harmonic with the engines vibrations caused the spring breakage. I appreciate the link to the alternate spring, but with the Model IV old system with the bellcrank splitter adding a counter acting spring is actually easier than removing both springs and raplacing them with lighter springs. Paul's experience was exactly like my first Kitfox. Not an exact balance, but there was no tendency to go to full throttle if the lock button was inadvertently bumped and when setting idle, the spring tension on the throttle arm seated it firmly against the adjustment screw. I think that is the issue I have right now. I adjust and who knows if the cable is tensioned to the arm.

[HighWing]

I did the deed. I received the original factory springs from Lockwood and installed them with the counteracting spring at the bellcrank. I was finally able to set a predictable, reproducable idle stop setting. I think I have corrected the engine shut down after landing issue. My counteracting spring exactly eliminates any throttle movement tendency.