Richard39

My Feedback: (14)

I have a good running MLD 35 that just recently developed a problem... The throttle arm will not fully close to idle or close to kill engine... I had to run engine at mid range to empty fuel tank last week in order to land... it would not lower to idle or close ... Mechanical kill..... took it home and everything worked properly... took back to field today and everything worked fine at home but at the field the carburetor continue to run in the mid range regardless of what I did to idle or kill engine.... ( will run on up to wide open but will not come down to idle).....

Throttle arm is not connected now to anything but still will not come down to idle? It needs 1/4 inch more movement.

We worked on it at the field and could not find anyway to lower the throttle even with it disconnected from servo... a friend suggested that the spring on the throttle (on the other side of the carburetor from the arm) was not strong enough to hold the arm tightly against the carburetor wall... After arriving home I was again trying to get more movement from the carburetor arm and as I pushed on the spring ...the arm moved about 1/4 inch to lowest position.. which is where it should be for low idle...

Can something be wrong with the Butterfly and if so how do I correct this problem...? Thanks for your help...

speedracerntrixie

My Feedback: (29)

I agree that the spring may not have enough tension, a new spring is easily found at your local Ace Hardware. Another thing to check is the screw that secures the butterfly to the shaft. The best way to adjust this is to loosen the screw just enough to release the butterfly then completly close the carb and re tighten the screw. I then clean the area well and apply a small blob of RTV on the screw to keep it from loosening again. You don't want to actually remove the screw as it has been swaged at the end to keep it from vibrating out. Completely removing it can damage the threads in the shaft.

Richard39

My Feedback: (14)

Thanks for the reply... I believe you are correct and I will follow your suggestions.... thanks again.... Richard

Richard39

My Feedback: (14)

I have the carb in my hands now and I do not see how to replace the spring if I first do not remove the butterfly.... am I not seeing this correctly...? is the shaft that the butterfly connected to designed to come apart in 2 pieces.... Thanks...

ahicks

My Feedback: (2)

You really don't have to use that spring's tension, so if you can't figure out how to reinstall it's not too big a deal. Many of us release the tension and control the carb opening with the servo. The preferred way (with or without tension) is the subject of much debate, and pretty sure you don't want to get into that here.

The more important thing here is that the spring stay in place. It will help prevent wear on the shaft and butterfly due to rattling when run without.

I'm betting the butterfly is loose on the shaft due to a loose screw. It doesn't happen often, but it does happen. That's easily fixed/checked with carb in hand. If loose, just recenter the plate on the shaft by closing the carb completely and assuring yourself the plate is fully closed. Then tighten the screw. I would use a drop of red loctite on it but there may be differing opinions there as well. The point is it must be secured to prevent this from happening again. Note that the shaft is easily bent or broken if you try peening the edge of the screw...

Richard39

My Feedback: (14)

OK ... thanks for the help... will check it all again....

Richard39

My Feedback: (14)

After doing all as suggested.... I again checked the screw holding the butterfly ... it was of course tight... I then loosened the screw just a hair and guess what.... the throttle jammed.. I tightened it again and it worked correctly... so I am going with that being the problem and fly the model tomorrow... I am sure all is well and will fly it until it has a problem which I hope will be many more flights.... Thanks... Richard

Truckracer

My Feedback: (19)

You might want to check the throttle for end to end play in the carb bore. Do this with the throttle open. Also look closely at the area where the throttle plate intersects the shaft and the carb bore or on each side of the throttle plate. Look for excessive wear on the carb bore in this area .... the throttle plate will eat its way into the bore near the shaft. In some cases, the throttle shaft can move from side to side due to wear and it can jam partially open. Manually recentering the shaft will temporarily allow the throttle to move and close normally. If there is excessive wear, the only cure is carb replacement. The usual cause is spring removal.

Richard39

My Feedback: (14)

Truckracer....The spring is and has been on the throttle for a long time but is weak... I cleaned and checked the bore as you mentioned and did not see any unusual wear patterns but I am going to fly it for a while and see what happens... I plan on purchasing a new carburetor soon if there is any problems while running the engine... The screw was loose but just a little and when tightened all works smoothly.... Thanks...