The spark arrester dose what its name suggests it stops bits of red hot matrial flying out of your exhaust, while i was riding my tenere around the states i removed the arrester ever now and again to let the crap blow out, as a build up can cause a lack of power and poor responce from the throttle. I was also warned not to ride in the state forests with out it as it could cause a fire..... a state ranger pointed out a notice to this affect.
Depending on how your XT is jetted you may find a lack of power with out it as it also works as baffles for the exhaust. hope this is of help Skip
Do the best you can with what you have,
A stranger in a strange land now heading North South East West to.....