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Old 05-29-2008, 07:59 PM   #1
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Default Help Setting Up Carb Throttle Linkage

Hey guys, I need help setting up the throttle linkage on my car. I think the collar might have slipped because when I brake the car shuts off, I already tried adjusting the idle screw as well as the throttle trim on the TX with no luck. I went ahead and looked at the AE manual and tried adjusting the linkage, just cant find the right spot and I dont really understand what the manual means by 1/16" on the throttle linkage. Can anyone point me in the direction of a good guide on how to do it or tell me how to do it? Thanks
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Old 05-29-2008, 08:42 PM   #2
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The linkage looks like this

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Old 05-30-2008, 01:26 AM   #3
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There's no way this is a linkage problem. Adjust your engine idle.

There can however be a linkage problem on top of that, your servo could be keeping throttle open on neutral, but letting it close when you brake. That's why it works until you brake. Linkage should be trimmed so that when you're on neutral, the throttle slider is resting on the carb idle screw, not on the linkage, there should be a 0.5-1mm gap on the pulling side of the throttle rod, and the spring should actually push and hold the throttle closed. You should neverever use throttle trim to adjust idle speed, that's one of the most stupid things lots of newbies do. Think what happens to this newly "adjusted" idle when you brake... bingo, throttle slider still closes until it meets the idle speed screw. The thing you want to use the throttle trim for is to create this gap I mentioned, so that the throttle IS in fact resting on the idle speed screw at neutral.

The fact that you turned the idle speed screw and it didn't help, can only mean 2 things: 1)you need to turn it moree or 2) you need to fix your idle mixture, it's either too rich or too lean. The engine should be able to idle at least 10 seconds without dying, then it could slowly load up and die at 20-30-40 seconds.
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Old 05-30-2008, 01:32 AM   #4
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Keep in mind this can also be the clutch. A broken spring or shoe could be the problem....
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Old 05-30-2008, 03:22 AM   #5
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Thanks for the ideas guys, I "reset" my throttle linkage to what it was when I first got the car based on some pictures i had of where the linkage was sitting in relation to the brake disc, carb, etc. I estimated the location, set the throttle linkage there and it fired right up. Still dies when I brake but thank you for explaining to me just where the gap should be, definitely makes more sense now. So 1/16" gap in the carb is what I should AIM for with the throttle off and resting on idle needle? Which way do I need to turn the low speed if its dying out? Less fuel right? Sorry for all the questions, first RC car. So for the throttle trim keep it at neutral on the TX

Lastly on a side note, do i need to cut a hole in my windshield and rear windshield on my new body for cooling? Or is it not necessary?
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Old 05-30-2008, 05:13 AM   #6
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yes cut a hole out for your motor to cool off, or you will overheat premature

also when your car is started hit the brake....does the idle change?
if so then its a set up problem, wether in the linkage or your radio!

(watch the linkage when applying brake, does it push the carb in?)
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Old 05-31-2008, 01:54 AM   #7
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Hey guys, so i got it to fire up but it still dies out if I dont keep the throttle going and seems sluggish, I'm guessing its a problem with the linkage. I dont get how to keep it from moving the throttle when I brake it just seems unavoidable since the servo spins the other way.

Olev: so what would you suggest be my steps to setup. Turn my TX throttle trim to neutral (center), back out the idle screw all the way until the valve doesn't move left and right (so the screw holds it) then adjust the linkage so with the TX on and RX on at "idle" there should be a gap between the linkage and the sleeve?

Does that sound about right? Thanks
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Old 05-31-2008, 02:33 PM   #8
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So I decided to start from scratch and re-adjust everything. So I followed Olev's guide. Turned on my TX, RX and set my throttle trim to neutral. Turned my idle screw in/out enough to where it is holding the valve from moving horizontally. Adjusted the linkage so I had a 1/16" gap. Voila, the brakes no longer mess with the valve. Now onto full throttle. On full throttle the gap was very small, so put it on full throttle and shut off the RX, thereby locking it in full throttle. Following the AE manual I adjusted the linkage till it was just about almost open. Turned the car back on and I have the 1/16" gap still and no pulling when braking. Now just need to test it outside. The LSN set to flush with the collar is that good base point to start from? Thanks, everyone, hopefully it starts running well again.
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Old 05-31-2008, 04:39 PM   #9
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Took it out a few minutes ago. Yay, back to normal, idles and brakes perfectly fine. The idle was a little high at first so I backed out the idle screw a little, I may do it a little more so it sits still, creeps a little, I think that's bad for the clutch? Thank olev for clearing up the 1/16" gap thing, makes way more sense then the AE manual and everyone else for your input. I made sure not to touch the TX throttle trim at all. Now to tune it so it screams.

On a side note; I did the "spit test" and the spit took well over 10 seconds to evaporate, I did only run it for about half a tank so I'm assuming it wasn't up to operating temperature, I'll do further tuning and testing later on. I'm fine running rich since its better then being lean.

Thanks Again guys.
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