Hi guys, I need some help hooking up my throttle control rod. I have a super tiger 40 ringed engine. when I hook up the control rod to the engine and then adjust it to the servo, it closes the carb like it should but to give it throttle ( to open the carb) it only opens a little over half maybe 3/4. I've looked and tried everything I can think and can not make it open all the way up with out it changeing the carb at the closed setting. I'm new to setting one up and cant seem to figure it out. The transmitter is a Hi Tech 4 ch. with standard servos, not sure of the #'s on the servos. I hope some one can help me. thanks for all the info you can give..

i'm not familiar with your radio........does it have EPA (end point adjustment)?
if not, you can try a servo horn with more throw and adjust from there to get the low and high to a happy medium.
start out with the throttle servo set to center, then connect to your carb and adjust the length so the barrel is in the middle of it's opening.

if you have EPA though it's really simple......you simply add more throw by upping the percentage of your high end travel...........

here is some info, and i'll look for more
http://www.ronlund.com/throttle.htm

here is another good article for you
http://www.skyrangersmodelflyers.com/article.php?id=53

it does'nt have EPA, not a digital/computer transmitter. the servo horn is a basic round one. would it be better to use one with arms ? thanks again for the help

yes.........the round ones will usually not give enough travel.
start out centered and play with it from there........it can be done as we had no choice back in the 60's and early 70's..........all our linakgaes were set manually............

thanks guys for the quick responses and all the help

Since you are short on "throw" start with the pushrod connected to the far outside hole of the servo arm and whatever point you presently have it at on the engine arm. If this still isn't enough total throw you either need a longer servo arm or to move the throttle arm attachment closer to it's pivot point. This is actually the proceedure you will need to adapt for ALL of the controls surfaces as well.

All the above is true and will help. But you can still screw the system up and defeat the system if you don't follow one very simple rule.

When the throttle stick on your transmitter is at 50%, the angles your pushrod makes should be at 90degrees to both the servo arm and the throttle arm. If you haven't rigged the system to do this, you've probably killed the carb opening/closing properly in one direction or the other.

If you don't setup the pushrod to the servo arm, and the pushrod to the throttle arm correctly, you start off in a lose lose situation before any of the other advice can help.

Start out with the transmitter stick at exactly half throttle. Set the throttle trim at center. Now hold the throttle so that it is half open. Or half closed if you're a "half empty glass" kinda guy.

Now route the pushrod so that it makes a 90degree angle with the throttle arm on the carb. The arm can be loosened on the carb and tightened at that right angle. And should be. You want the throttle opened half way with the throttle arm at a 90 degree angle to the pushrod. If you don't have that right angle, then when the pushrod pushes or pulls, it's going to not have either enough push or enough pull. Yeah, the pushrod will move back or forward enough, but the throttle arm has a rotary motion, and it won't be moved "around" enough in one of the two directions.

Same thing is true of the servo arm. The servo moves it's arm in a rotary motion. If the pushrod isn't at a right angle to the servo arm when the servo is sitting at 50% throttle, then the pushrod isn't going to be moved equally in both directions.

If either the servo arm or the throttle arm is NOT at a right angle to the pushrod when the servo is at half throttle and the carb is half open, you can wind up with what you're seeing. And no computer radio in the world can do anything about it if it's rigged badly enough.

Just last week, one of our more experienced guys who has been flying A LOT for the last 4 years had a newly purchased airplane that wouldn't throttle right. No matter how he set the endpoints or changed the centering in the radio, he could not get the TX stick to open the carb completely. I heard him say the only solution was to swap out the carb. It was an effort to convince him to let me adjust the rigging. The EPAs had to be brought back to 100%, the centering centered, the stick put to 50% and trim centered. At that point, the servo arm was about 3 teeth off and the throttle arm on the carb was about 50degrees from a right angle. That carb had no hope of ever opening fully. We set the servo arm to a right angle with the pushrod and unhooked the pushrod so we could adjust the throttle arm at the carb. Held the carb opened half way. Set the throttle arm at a right angle to the pushrod and tightened it up. Tightened the pushrod at the servo arm and were good to go.

After all those words........ this may or may not be your problem. But it often is. And worth a look.

................edit to add pictures and description.....................
The picture on the left shows a smaller (weight consideration) throttle servo by itself to the right in the picture. It's servo arm isn't exactly at 90degrees but is close to it. (I setup the throttle on some models to give linear power advance, not just work linear. So center stick on the TX doesn't usually wind up being a good example of this topic.) The picture on the right shows the throttle barrel opened about halfway, and the throttle arm is about 90degrees to the pushrod.

OK, here's a picture.

Rig the servo arm and pushrod like it's shown with the green pushrod and the connection at "a". That's what you want with the TX stick at half-throttle. That way, when the TX throttle stick is moved up or down the pushrod gets pulled or pushed about the most it can be. And it'll be pushed the same amount that it's pulled.

If for some reason the rigging looks like "b" (with the blue pushrod) when the TX stick is at half-throttle, you got problems. If the stick is moved so the servo arm rotates counter-clockwise, it will pull the blue pushrod a very, very short distance. And no matter how the carb arm is rigged, the pushrod end at the carb is barely going to move.

Same relationship happens at the carb arm.

So you want both ends of the pushrod to make a 90degree angle to whatever arm it's connected to.

thanks rock for all the help. that really helped! I think I can get it now..