I would have to agree with schwim spend the time checking out what you already have all the info is available on this site, I fitted the YTZ7, better starter leads but first check the original starter motor rear bush is not worn, it was in mine, and finally sort out the auto de-compressor and if both you fueling and generation is all good it should start easily of the button. A Honda CBR600 F4 starter will fit a 2003 fe400 but it is longer giving it a better turning power but a modified bracket is needed to make it fit, I got a F4 starter off EBay for less than a tenner but have not had to use it yet as I have set the bike up like previously mentioned