We thought it was a fuel problem at first. The cap is drilled out and the dual pingle is on it. The plugs have been gaped tighter at .025
Runs 35mm carbs with 140 mains CEL needles middle clip. Has trouble at the very top of the RPM band. I have been helping on the phone but the 140 mains at 5,000 feet seemed lean. What are you ported guys running at 5,000 plus feet? I know I have some Colorado motors running at this elevation but cant find my notes.