Dave, A few years ago I've had similar problems with my ST 2500, as well as my stepfather with his ST 4500. We got a recommended set-up for AnnMarie Cross from Hobbico at that time. Follwing the set-up all our problems were solved. My ST 2500 is mounted sideways in a CAP 231, My stepfathers in mounted inverted in a Bryon RYAN STA. If you want to try her set-up before you change carbs, I put it out yesterday in the fun-fly section. Look under "super tigre vs.". At the bottom of the 1st page is my post describing her set-up. It's a timely set-up but it worked great on all my ST's. LOL

KEVIN