Mainly because I'm one of those people who likes to work on my own stuff and I have built a Wren from a kit, and I was pretty sure from the people I had talked to that it was an issue with the combustion chamber, something that I could fix (or get a replacement part for) quicker and as cheaply as sending it to China and back. Joe charged $80 to ship it to me the first time and the warranty only covers parts, not labor.

Russ,
Don't worry, I don't intend to do any balancing or precision machining, if an unclogged fuel ring and straight combustion chamber doesn't fix it I'll send it to someone more qualified.

Mike