No I haven't seen it go into fourth, what is the minimum speed for fourth regardless of throttle position?

There is a hill near my house, that will probably get it into fourth, and if I put the bowden cable all the way in I may be able to keep it there.

I'm thinking maybe the valve body is clogged, with debris, I may as a last ditched effort take it out, take all the removable components out of it and have it hot tanked.