That's because motor tuners have hundreds of motors to go through and get the ones that are good and junk the rest,they don't get good #'s on all their motors,there are manufacturing differences that you just can't overcome on some motors,unfortunatley it's just one of those things that we have to deal with,when I get a motor that just won't run no matter what,I usually just chunk it and get another one,or turn it into a practice motor,I've probably got two or more practice motors for every good race motor.