7 tanks sounds too little, these motors are a dog to break in. Had two GRP tuned motors. I stuffed one of them up during break in. Got the motor that my mate had that put in a bunch of tanks, I put in another 5 or six on the track leaning out after every tank, started rich. After the end on the runs the motor was not idling so I thought the rod was going, not an issue. Closer inspection the I elongated the piston where it connects to the con rod. Bottom line motor was still ot run in!!! My other one I had a run away with, blew piston and sleeve, got a knock on the reciever, very sad mate. Nice motors and cheap compared to NR, dead easy to tune. Just be patient man