Have had a few trikes over the years but never got around to modding them or anything....had a fox body mustang I modded and raced so the atc or motorcycle engines are a little foreign to me. Did honda ever put counterbalances on any of the atc's? I have an old 81 200 and it has been rebuilt before I got it with a new crank and the works I guess but it has the typical vibration they all had. How long do they last usually with the vibrations? When I think about it I'm surprised they are so reliable without counter balancing.