You need a healthy battery pushing 12Vs to make the ES work. Not sure about yours but my 2000 450es Foreman use to act up and not shift sometimes and removing a fuse from under the seat and reinstalling it fix the problem for some reason.
I heard of a angle sensor causing this also but Honda improved on it and a 2005 should have the improved version.
2001 Yellow 500 H.O
No Plastic roll cage
5.25 gas tank.
2007 350 Grizzly