With the pinion it doesnt move. There are no force in the engine when it starts doing this. Maybe there is some crap in the engine that creates this "cogging"?

Before it worked OK but after a while this happend and I thought it was a problem with the clutch. The first error I had with the car was a faulty adjusted clutch! So mutch for RTR! I burned down the clutch within a cuple of minutes. Second "problem" was a exploding tire (my own fault, I think). Now this...

I have two other Traxxas products that I NEVER have had any problems with so this is not funny at all. You think you buy a good product and this happens. This car have not drained it first batteries yet...