I've got a Morgan Carbtune, which works well on my 4 cylinder bikes as well as my airheads (on the airheads you have to hang it upside down as it effectively changes its scale/sensitivity that way). The original TwinMax was used by alot of folks, so I think that it can be made to work, though when I found the schematics for it I noticed several ways it could be improved. One critical thing - at least with the first model I saw - is that you've got to make sure the battery you are using is fresh - the accuracy and resolution is significantly affected by dropping battery voltage as it didn't use any real DC regulator in its power rails.