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Rv14A throttle

Dennis Harm

Active Member
Just wondering if anyone has had a stiff throttle movement the first 1/2 inch or so. I have the avstar fuel servo and Vans stock throttle cable. The stiffness is not in the cable as it was smooth before hooking up the throttle arm, thanks Dennis
 
14 throttle

Hi Ron, removed the throttle cable and throttle arm moves free. Do you have the offset throttle arm or did you change it out to straight arm? Not sure if the offset arm would cause friction somehow. I know Tim Olsen changed his out to a straight arm. Thanks Dennis
 
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I'm quite sure I used the arm Tim used but I have a poor memory. I have the cowl off because I'm doing the nose gear SB so I will have a look.
 
Throttle stiffness

Hi guys, have ordered the straight throttle arm from avstar and will see if that helps. lr172 what is heim . I’m assuming it’s the mixture arm connected to the throttle arm. Thanks for the reply’s, Dennis
 
Throttle arm

Just a update on the avstar throttle arm. Installed the straight arm I received from Avstar and it made a big difference. Movement is now smooth Thur out the travel on the throttle. Thanks Tim O for the part number and advice
 
Throttle arm

Part # is AV2522004. You can order on Avstars web site.you’ll also need a different bolt as you don’t need the spacer any more. I tkink it’s a An3-10 that fits.
 
Same problem when hot

Just wondering if anyone has had a stiff throttle movement the first 1/2 inch or so. I have the avstar fuel servo and Vans stock throttle cable. The stiffness is not in the cable as it was smooth before hooking up the throttle arm, thanks Dennis

FWIW, I now have the same problem, but only when the engine is hot. Ordered the straight arm today.

After looking at the geometry, I'm not sure why the kit did not include the straight arm to start with. The cable aligns directly with it and does not require a spacer as it does with the offset arm.
 
Learned more about this from Avstar

After installing the straight arm, I still have the problem for the first half inch of throttle travel when the engine is hot, as during a refueling stop. When cold, it works fine.

I called Avstar and found something I did not know. When an engine with their servo is shut down and there is no fuel return line, pressure builds up between the servo and mechanical fuel pump. On my Dynon system, it got to about 150 PSI and then a red X appeared. Avstar says on their system, this high a pressure results in a side load which ultimately causes the problem I have -- hard throttle for the first half inch or so. They recommended that prior to start, after the engine instruments are working, to move the mixture forward to drop that pressure to 60 or below. This releases the side load and lets the throttle run smoothly again. I tried it today and it works.

As an FYI, I have 890 hours now on the experimental IO-390 Lyc sells and this problem did not occur until recently.
 
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