Rebuilding problem

[Naushad]

Hi

I hope you guys can help me.

This is more of a technical query.

I have rebuilt my bmax4. However when I press the throttle it stutters as it moves. However if I press the throttle gently and gradually it move smoothly.

This might be a newbie question but I'm getting back into rc afte a very long time.

I tried adjusting the front and rear diffs but this did not make any difference. The pinion appears to be gripping with the spur and there's no spin.

I'd really appreciate your advice.

Regards

Naushad