Have you called Butler about your problem yet? If they assembled the engine for you and shipped it complete, they may repair it for you at no charge except for the shipping. Give David or Jim a call and see what they are willing to do.
They did some machine work for me and I assembled the engine. I encountered a problem that we both could have contributed to. I was polite and waited to hear from my local machine shop as to the depth of my problem. David worked with me and helped me get the issue resolved as well as helping with replacement parts.
