[Noob question] Engine turns on but no more throttle response

[Aeromotive]

Hi all.

I'm new to the hobby. My model is a Kyosho DBX 2.0 which I got as a gift.
Last year I asked a question on the forums about a broken throttle servo horn, which I replaced after getting the parts, with the right part number in my manual.

After fixing this, I took the car for a spin and after 20 minutes of fine tuning my needles (the car had been stored for a while), the throttle stopped answering. I still got steering response and the engine was still on. However the throttle servo horn wouldn't move... the car was just siting still

Anyone knows what's going on? Did I break something while replacing my servo horn? How can I diagnose this? Is it better to take it to my LHS? I would love to get the car up and running again... looks like a silly problem. But is it?

Thanks.
Aeromotive.

 

[Jacks9930]

Take the horn off the servo and see if the sevo still move. If not you may need a new servo. If it dose move check the servo and horn for being striped.

 

[Aeromotive]

Thanks. I didn't take the horn off, however I did something similar. In the following picture you see the servo through a very small gap between the horn and the case of the servo. (sorry for the quality it's a phone picture)

I went to a very silent room and looked very closely at the servo while I hit the throttle. I couldn't hear anything, and the servo was clearly not turning. Is this a reliable test?

I'm guessing something is wrong with the servo itself?

 

[Jacks9930]

Try a differnt sevo.

 

[Justamattd]

agreed

 

[Zdragon71]

Yep seems its time for a new and better than stock servo. Get yourself a savox sc0251mg. Ebay has them for $38 free shipping.

 

[Aeromotive]

Thanks!
I just have a few short questions :

1) Is it possible that I broke the servo while changing the servo horn? Keep in mind that I lost throttle response after a 20 minutes run, which makes it pretty obvious to me (although it wasn't immediately after).
2) Is this easy to replace? No clear tutorial on YouTube.
3) Are there any compatibility issues I should be aware of? Any type or brand I should be looking for? $40 is no big deal, but I want something that lasts. However since this is an RTR and my first Nitro RC I don't NEED the best of the best One other thing is that the SC0251MG seems taller than my stock servo...
4) After fixing this, do I need to tune everything again (needles, idle screw)?

I appreciate the help!

 

[Zdragon71]

Savox, hitech, and futaba are three better or best quality brands. Rtr servos are crap. I'm surprised if any rtr servo last more than a few tanks past breakin. High end metal and titanium geared servos as the savox 1256tg and hitec hs7955tg are built to be repaired if they break but I've never had one quit working. Look at specs when shopping for servos and find one that is the same dimensions and at least 125oz inches of torque at 6volts. The savox sc0251mg is an 1/8 scale replacement servo. I run it on my tmaxx steering. I run Futaba S3305mg servos on my 1/8 scale buggy steering and throttle/brake. Never buy cheap off brand servos. Always stick with savox, hitech, or Futaba metal or titanium gear servos for best life and performance.

---------- Post added at 6:02 PM ---------- Previous post was at 6:00 PM ----------

No you dont have to retune the carb when replacing a servo. Although you may have to reverse the radio controls if it is backwards on response once you install a different brand servo. Your radio manual will tell you how to do so.

 

[Aeromotive]

Thanks Zdragon71. Anything to say about it being easy or difficult? Any tips?

 

[Childresshunt]

its normally not hard to replace a servo some are more difficult than other but u just have to sit down and look the car over and see what all u have to do to gey the servo out along with the lead. most ofthe time u just have to remove the horn and take the 4 screws out that fasten the servo to the servo mount and remove it. b4 removing the servo tho go ahead and unplug the lead from the cars reciever

 

[ND Kyosho]

Also make sure to connect your servo into your receiver correctly. Positive to the positive and negative to the negative. Many receivers dont mark the + (red) and - (negative) so check to see if its plugged in the same way as your steering servo since your steering is working. Even though it sounds obvious many people make this mistake. Replacing a servo is very simple.

To replace the servo first unplug the servo from the receiver. Look at how your current servo is installed as far as the direction its installed. Take the servo off the mounts that is holding it and put the new servo on the monts the same direction as the old servo. Plug the new servo into your receiver correctly. Then turn on your radio and the power to your rc. test your sevos to make sure they work properly. If they do, leave you powr on and set your radio/ controller down with the power on. When the power is on your servos are centered. Then install your horn in its proper location (varies by model of rc.) Check to see your servos are working properly one more time. If they are working properly you are finished. If not unplug the servo from the receiver and redo the steps again. I hope this helps

 

[Aeromotive]

Thanks for everyone's help. I just took off the throttle servo (took a few pictures to make sure I don't forget how everything was placed). Now I'm off to shopping for a servo...

Edit : still looking at the SC-0251. Case Size (LxWxH): 40.7x20x42.4mm. Is the 42.4mm really the case only, or does it include the spline? My current case height would be 36mm, 42mm with the spline.
@ND Kyosho : Not sure I understand what positive and negatives are. I only have one (triple) wire with one plug that goes into the receiver.

 

[Zdragon71]

Its case size not including spline. It can be a little taller than your stock one as long as there is extra room where it mounts and as long as you can bolt it down evenly. Most all 1/8 scale buggies will hold the savox servo.

 

[ND Kyosho]

Your servo has 3 wires that go into the plug that goes into the receiver. Should look similar to this.

Usually the side with the black wire is negative, in this case its brown which is also commonly seen. The side with the red and the other color is positive which also varies, in this case its red with orange.

Some receivers have a notch in them to "dummy proof" how to plug in the servo ends which sometimes dont have notches on the side like the one pictured above. Some receivers dont have the notch to "dummy proof" the connection in which case you may have to cut the notch off your servo plug if it has one. Below is a picture of a spektrum receiver that doesn't have the notches.

Notice where between gear and aux 1 has a -+? the negative black/ brown wire goes in the - side (in this case the left side) where the other 2 colored wires (positive) go in the + side (in this case the right side.)

Hopefully this makes more sense

 

[Aeromotive]

Thanks. I will look into that! Now off to choose the right servo. Any tutorial about the different characteristics? How to compare models? Amainhobbies suggested 3 models : 83.3 oz, 145 oz and 196 oz. Why would I take 196 over 145? And why not something else?

 

[ND Kyosho]

The oz is the amount of torque. The larger the number the more force the servo can handle. The there is the speed (0.XX sec @ 60 degrees) the lower the number the faster the servo. I always look for a metal servo that is digital. Most popular brands are HiTec, JR, Savox, and Futuba. Other good notables are Team Orion, and KO Propo (Extrememly expensive.) The servo in my 8ight t and xt2 are the HiTec HS-7955TG titanium gear servos. A servo I'm looking into trying is the Team Orion Vortex VDS-HV 2612 ultra torque servo. Both are available at amain at a similar price. I can guarantee the Hitec servo I have is great. I havent tried the Team Orion, but anything I have from them I have been very pleased with, and that servo looks very promising.

According to specs the Orion servo is much faster than the Hitec 0.12 @ 60 compared to 0.19/ 0.15 @ 60 and also has more torque than the Hitec 361oz compared to 333oz, and also cheaper. Also getting a metal servo horn is a good idea with a servo with that much speed and torque. Make sure you get one that fits the brand of servo you get.

 

[Aeromotive]

I'm guessing a faster throttle servo would mean faster throttle response (eg. pinching throttle for abrupt acceleration)?
What would more torque serve for?

 

[Childresshunt]

you want high torque for steering or if u have a throttle return spring

 

[ND Kyosho]

woops I'm thinking of steering servos lol. I should go to bed. If you want a new steering servo get that Orion lol. I have a JR ST126MG High Torque Servo in my 8ight t for a throttle servo. Its good enough and less than half the price of the servos I pointed out earlier. You may want to find a faster servo but if your not racing it would be more than enough for a throttle servo.

 

[Aeromotive]

...Most all 1/8 scale buggies will hold the savox servo.

But mine is a 1/10... that's too bad, it looked like a decent, affordable option (the SC0251MG).
For around $40 there's also the HS-5645MG (0.18 sec/164 oz-in @ 6V)
Is it really worth it to spend $20 more for a HS-5565MH (0.09 sec/194 oz-in @ 6V)? :\
(I don't race... I use my RC once every 2 weeks)