BK or Radio problem?
 

I have e-maxx with small BL motor and BK 7020 control with 4S batts (kinda mild set-up)

Here's what it does wrong. I'm not sure if it's a radio problem or controller.

Only when over 100ft away AND letting off throttle it is jittery or no-throttle until it gets closer OR I go back to neutral.

When running at close range it does everything right (even at WOT)
Wehn running WOT it does everything right (even at far range)

If it is over 100 ft away and you never let off the gas it's fine. If you do let off the gas it will be very jittery if the vehicle is allowed to stop, if the vehicle isn't allowed to stop there's steering perfect, but no throttle until stopped.

Is radio problem or control hitting some safety or cut-off?

I have eliminated the TX , RX and the trouble was in a different e-maxx before this with 12 cells and no seperate bec. Now I have a different 7720 and have run it with and without bec. It doesn't seem to act up on 2S like it does on 4S. $s also seems to be a bit worse than 12 NI cells were.

The only thing that is common between the two truck is the 2PL Futaba TX and the chinese motor 56x60x2200 rpm. The other thing that's the same is the BK 7720 (even though it is a different one) They both do it.

I think it is likely just radio noise especially as it is a distance thing - potential solutions:

1) run around after your truck so you stay within 100ft
2) try to relocate components to keep attenna away from interference
3) minimize interference i.e. braid motor wires - ferrite rings
4) buy new radio and go 2.4...

Option 1 would be funny to watch and keep you fit...

NO. 1 sounds most beneficial. Thanks.
Reading up on ferrite rings right now.
Too cheap to buy a new radio since I use it on 10 models.

I did twist motor wires this time , not the batt wires yet.

I just hooked the packs in para rather than series and the problem completey goes away , it runs good even far away.

Next step is perhaps to use a smaller and/or lower KV motor with the 4S. I had planned on using 6S on this set-up , but haven't got that far yet.

Back to 4S with all twisted wires and if allowed to go jittery at far distance I can keep it held at WOT with no motor movement at all (just steering)

Only when releasing throttle to Neutral will it start again. Seems like a LVC somewhat. I don't think it has one though? Definately the higher voltage is worse.

I put a smaller and lower kv motor and smaller pinion gear just to help diagnose this. I find the rotor is spinning inside itself.

That's not good. I figured it had to be something to do with the motor and RPMs because it ran ok on 2s.

The old motor is ok, it's the new lower kv smaller motor that has the rotor spinning. It's brand new, but I've had it for many months. I may take it apart cuz I have no idea how rotors are put together. The outside of it spins smoothly , but it is not spinning the shaft unless it's on a stand on the bench.

I think my problem is radio interferance, but it only shows up as the power level increases. I suspect I can run a small motor geared low on a 6S and have no trouble. I will find another low kv small motor if I have one.

I found a different motor:

Original 36x60x2200
badrotor 36x56x1800
new one 36x50x1500

Preliminary testing shows the new smaller/slower motor to be perfect with 4S power. I'll put in a 6S and check it at all ranges.

What to conclude if it is perfect?

bad motor, esc cutting out, or radio interference.

Well, I ran with the slow little motor and all works perfect even at a far range.

thats good to hear - now you can start enjoying the truck!!

I just got in from running the 6S and it still works perfect. I need bigger motor to enjoy, lol. :yipi:

I've been running with the small 1500 motor many runs and all is perfect.

Still don't know what to conclude, I don't think any one component is "bad"

I just replaced motor with a bigger, but slower one. As son as I get some weather I'll test it. I suspect it'll be fine until I gear it up to start making some speed. It's now geared to match the speed of the small 1500 kv motor.