Kraton Kraton 4s cutting out after jumps or shock to chassis

[Alan George]

Hey guys, I'm new to the forum scene and I've only just got back into rc after a 20yr break so brushless/lipo is new to me. I recently purchased a kraton 4s and immediately made a good deal of upgrades. The first few runs were faultless but I took it to a bmx track this weekend and after 1 pack and 1 or 2 hits to the front end it started cutting out (almost like LVC) but everything was running reasonably cool. Battery status was all good at the time and I hadn't been running in water. As far as upgrades go I've swapped out the stx2 system and fitted the dumborc, jx EcoBoost servo, 3.8 badlands which were slightly smaller diameter than stock minokawa so I changed pinion from 13t to 15t to compensate. Ive also changed out the ec5 connectors for xt90. Everything else has been suspension related. I've cleaned and dried out any moisture and re-installed the original stx2 system. It doesn't seem as bad now but the problem is still there. Any ideas guys as I'm suspecting the esc but don't want to go down that road if I'm missing something simple. I'm a mechanic by trade and I've got all sorts running through my head at the moment, but I know there are a lot of people far more experienced than me at this so would really appreciate any input. Seems to happen either when I'm at full power or any shock to the chassis. Thanks in advance.

 

[slick2500]

Does the esc restart itself or does power the motor just cut out? If you are certain that your battery plugs are good then I would also suspect something internal in the esc.

 

[jondilly1974]

Did you get MX38 or 3.8 Badlands? The MX38 would be quite heavy. My guess is you are amp limiting or thermalling

 

[slick2500]

Did you get MX38 or 3.8 Badlands? The MX38 would be quite heavy. My guess is you are amp limiting or thermalling

I think he got MX2.8 Badlands, I don't think 3.8s are slightly smaller than the stock 4s tires.

 

[jondilly1974]

I think he got MX2.8 Badlands, I don't think 3.8s are slightly smaller than the stock 4s tires.

Badlands 3.8 - 149mm
MX38 - 176mm
MX28 - 128mm
Minokawa LP - 155mm

 

[slick2500]

Badlands 3.8 - 149mm
MX38 - 176mm
MX28 - 128mm
Minokawa LP - 155mm

Damn, I guess the Minokawa LPs are larger than I thought they were.

 

[Scoot]

Hey guys, I'm new to the forum scene and I've only just got back into rc after a 20yr break so brushless/lipo is new to me. I recently purchased a kraton 4s and immediately made a good deal of upgrades. The first few runs were faultless but I took it to a bmx track this weekend and after 1 pack and 1 or 2 hits to the front end it started cutting out (almost like LVC) but everything was running reasonably cool. Battery status was all good at the time and I hadn't been running in water. As far as upgrades go I've swapped out the stx2 system and fitted the dumborc, jx EcoBoost servo, 3.8 badlands which were slightly smaller diameter than stock minokawa so I changed pinion from 13t to 15t to compensate. Ive also changed out the ec5 connectors for xt90. Everything else has been suspension related. I've cleaned and dried out any moisture and re-installed the original stx2 system. It doesn't seem as bad now but the problem is still there. Any ideas guys as I'm suspecting the esc but don't want to go down that road if I'm missing something simple. I'm a mechanic by trade and I've got all sorts running through my head at the moment, but I know there are a lot of people far more experienced than me at this so would really appreciate any input. Seems to happen either when I'm at full power or any shock to the chassis. Thanks in advance.

Like my Dad always said, " You got a loose wire kid."

I would power it all up, and start pulling on wires to try to duplicate it. Battery cables, esc wires, etc.... You could also do this under power with the wheels off sitting on a block or something. Next guess would be something internal to the esc like @slick2500 said.

 

[Alan George]

Thanks for the replies guys. I'm running the 3.8's which are slightly smaller than stock, I did try mx38's but was worried about the extra load so I didn't go with them. At the track it did seem like the esc was restarting as it took a few seconds to get steering back and then motor, but after having a look at it I took it on short grass and did some speed runs and it seemed to cut for just a second then power back on. I think your on the right track with a bad connector or loose wire though guys, so I'll have a look at that first. The other thing that I thought of was it sounded like the slipper was either worn or backed off, would that cause amp limiting if the motor was over revving?

 

[razorrc]

The other thing that I thought of was it sounded like the slipper was either worn or backed off, would that cause amp limiting if the motor was over revving?

No, if it is cutting momentarily, then almost certainly a bad wire connection. Any of the ESC protections (LVC or overtemp) would cut the power permanently to the motor until you turned it off. I'd check the parts you changed, like the XT90's, or the receiver you installed and the wires on it.

 

[jondilly1974]

I’ve had ESC amp limiting that doesn’t need to be restarted to regain full speed, but that’s not what he has going here. This surely sounds like a bad connection between the lipo and ESC. Or just a bad ESC.

 

[Alan George]

Managed to pull it apart and have a look during my lunch break today. I found the power cable from esc to motor cooling fan had chaffed through on both + and - and looked like they might have been arcing on each other. I've got a new lead ordered and I'm gonna solder a new xt90 to the esc power cables and hopefully it'll solve the problem. I'll let you know the outcome once I've had a chance to run the car. Thanks again guys ?
Got that wrong it was the lead from the receiver aux to motor fan.
Got that wrong it was the lead from the receiver aux to motor fan.