Hey all, New guy here. I bought my son a helion invictus 10mt and It cogs really bad even with a fresh 2s battery in it. I'm fairly new to rc monster trucks so bear with me. Is there anything I can do to help with the cogging? Mods or upgrades?

Because its sensorless, I assume.

It is a sensorless esc + motor. In sensorless systems the esc reads back electro magnetic frequencies (EMF) coming back through the motor wires to determine the motor's position. The motor has to be spinning a certain amount of rpm to generate enough back EMF for the esc to read. So from a stop the esc has a preprogrammed startup algorithm it uses which is a one size fits all algorithm specific to the esc, not optimized for the vehicle and motor so it may not be that smooth. Now if this algorithm is set to spin the motor to 1000rpm in .5 seconds and the motor only reaches 500rpm the esc can't sense the back EMF so it runs the startup algorithm again and you see that as cogging. My numbers for the algorithm are made up just to demonstrate the principal.

One way to reduce cogging is to reduce the load on the motor by lightening the vehicle or changing the gearing to slow it down. Another way is to add more power with a higher voltage battery or a more powerful motor. The esc in your truck is a generic rebrand or copy, a higher quality esc from Castle, Tekin, even Hobbywing should have a better startup algorithm that would reduce cogging.

Cogging doesn't exactly hurt anything though. It just indicates a less than optimal startup algorithm and/or not the best motor/gearing/voltage choice for the vehicle. As long as the motor and esc temps are within limits the cogging isn't damaging anything.

OK thanks. In a nutshell I would be better with lower gearing to help the motor or get more power.