I'm assuming you are asking about the speed sensor on a 2006 or earlier Burgman 400 as you didn't specify the bike and that is the only Burgman with the sensor on the front wheel (at least in the USA).
Yes it is a good idea to lube the speed sensor on the Burgman 400. I use high temp wheel bearing grease on mine. I gently pry the seal out, clean the old grease off the rotor, apply a layer of new grease, replace the rotor in the housing and tap the seal back in.
If you are asking about a different scooter then I can't say if this would be true or not.