I know I am going to get an argument on this one, but the problem is your engines.

The ninja engines had some growing pains. The OS TZ engines are notorious for rod problems. Especially if they are modified. You don't hear about these problems with Novarossi engines. I have never broken a rod on my Sirio .12 engines either. There is a reason why some engines cost more than others. This has been my observations over the past 3 years.