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throttle seems to be binding

M

moll780

Well Known Member
The throttle cable on my 9A (0-320) seems to be binding someplace.
I unscrewed the lock to remove it as a possible culprit but it still seems to be binding.
I haven't taken the cowl off yet but I wanted to ask the community for ideas of places to look.
logically ill check the cable itself and the linkage at the carb but any ideas before I take a deeper look this coming weekend would be helpful.
thanks!
 
Cables wear and must be replaced. Heat & friction gets to them.
If your doing a lot of throttle movement like we do flying formation, they wear quickly. We have cables that wear out in a couple hundred hours. We have tried many things to increase their life. But they fail regardless. Starts by increased friction, then a ratchety feel, then lockup.
 
My throttle seemed to jump from working fine to needing loads of right arm to push and pull.
Could it be something in the carb itself? this is my real fear... replace a cable, ok no problem. carb issue? now im scared.


Kahuna said:
Cables wear and must be replaced. Heat & friction gets to them.
If your doing a lot of throttle movement like we do flying formation, they wear quickly. We have cables that wear out in a couple hundred hours. We have tried many things to increase their life. But they fail regardless. Starts by increased friction, then a ratchety feel, then lockup.
Click to expand...
 
I had the same problem on a 172.
The accelerator pump went bad, and required a lot of force to push the throttle in.
 
Disconnect the linkage from your carb and you can eliminate that right off the bat. My bet is it will be the cable itself, but you never know.
Most failures I have seen are due to heat.
Pay close attention to the cables proximity to your exhaust. These cables will degrade in the area they are getting exposed to excess heat. If that is the case, you can rework cable routings or use heat shields to mitigate it down the road.
 
first, lube the friction lock

my first check would be, remove the friction lock and apply mouse milk lube at the plastic ferrule.
 
I'd remove the lower cowling and go from there. I recently experienced a similiar problem and discovered the scat tubing from the carb heat crossover to cabin heat was a little too close to the throttle linkage on the carb. Inhibiting just enough that I wasn't getting the last 1/4" of full throttle. But as suggested earlier, if your linkage isn't binding anywhere, disconnect from the carb and check how smooth/rough the throttle cable will be.
 
Kahuna

My 7 has the original cable 600 total hours 400 in formation still smooth. should I worry? Gene (Whiskey Flight)
 
Throttle tightness

I had the same problem in my RV6. Turned out the exhaust heat was causing expansion which made the cable get tight during flight. I put firesleeve over it and wrapped in silver foil tape. Sleeve goes from firewall to the bracket that has the nut that holds the cable in place by the carb. No problems since. Coincidentally, my engine is an 0-320 too.
 
Throttle binding

Had to replace my throttle at about 300 hours. Upon removal noted that there was thermal damage due to exhaust heat. Replacement Throttle cable provided with thermal protection and has lasted another 200 hours without problems.
 
I'm on my fourth cable in 1900 hours. I have used heat shields and fire sleeve to protect the cable with disappointing results. I fly LOTS of formation. My latest cable is protected with a fire sleeve with cool air ducted into the sleeve. So far it's working, but I keep a spare cable in stock just in case.
 
Check your engine ground cable.

If the engine is not grounded adequately, when you energize the starter the control cables become the ground wire. The result will be several hundred amps flowing through the cables. This can lead to "sticky" movement of the controls .
 
I had a sticking (almost locked up) throttle early in phase 1 when the engine warmed up. After much head scratching I removed the carb, placing it on the oven (When the spouse wasn't looking) and was able to duplicate it. Sent the carb back to Aerosport where they determined that the butterfly hole wasn't properly deburred from the factory. So much for " certified" parts.
 
so I started the CI this weekend and after removing the cowl I was able to move the cable freely from the carb. I tested from within the cabin and also moved freely.
When I initially discovered the issue I sprayed a little LPS downstream of the locking collar. I am thinking it worked its way down the cable and freed up any binding.
Otherwise I have no idea where exactly the issue was.

Should I just replace the cable? it seems free moving now with no "gritty/notchy" feeling. nice and smooth.
 
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