if the livespan of your engine is something you don't worry about, leave it as it is.
but especially if you plan to ride in dusty environments i would strongly recommend to fit an air filter box. you can use any of the following xt600 models: 34L, 43F, 55W, 2KF, 2NF (tenere 83-85, xt600 84-89).
it should be possible to find a second-hand one. you may ask moritz kullmann (motoritz @ gmx.de).
tell him i send you.
email address removed/modified by Grant for security
[This message has been edited by Grant Johnson (edited 03 April 2002).]