There is a Super Tigre thread dedicated to setting up these engines, in the glow engines area. You really should check it out, your problem may already be adressed. This is a factory representative answering the questions. I have found his techniques to solve all of my ST set up issues. Once they are properly broken in and set up, they are very reliable engines. Just plan on spending some time breaking them in. The owner's manual is available on the Tower site for that engine in PDF format, you may want to start with the manual.

Good luck.