Originally Posted by expatbrit
Still -- definitely got the unit FUBAR, showing all the symptoms of the buggered head unit from the WR forum. I just haven't seen it reported anywhere else but there, and it's a pretty serious issue.
This is a problem with (at least one) WR450 also, my riding buddy's speedo went apeshit in much the manner you describe, reading crazy high. In his case it just happened, there was no dead battery or other event to point your finger at.
Looking at the 250 and 450 components, they are very similar.
You may want to expand your Google search for solutions to include the 450; though I don't think he ever solved the problem.