Update - I thought my wonderful 120AX was making a little extra noise, seemingly coming from the rear bearing. I took it apart to check things out and found a slight rub between the con rod and the crank case. I did a separate post (which I'm learning not to do) and ended up calling Hobby Services for advice. They advised to send it in. Within one full day of their receipt of the engine they shipped me out a brand new 120AX engine.

Obviously we don't live in a perfect world, and things don't always get manufactured perfectly - it happens to everyone. OS/Hobby Services offers very, very strong support and warranty service along with their amazing products.

While I am trying my best to take the suggestions of others and not limit myself to a single brand, OS makes it very difficult to look elsewhere. For ease of use and tuning, reliability, and exceptional service, OS engines has the market cornered. I understand and agree that there are other engines on the market, and depending on what you want they might even be better options (like a YS for power, Saito for light weight, etc.). But, for this beginner who needs nothing but practice and airtime, OS has been the choice for me, and I am one satisfied customer.