I changed oil and filter and switched to Castrol Actevo 20-50 because of a recommendation. I fire it up (XR650R with under 1000 miles ) and hear a buzzing sound from the oil filter/pump housing. I did a search and see that it is pretty common with thicker oil. I ride 5 miles total to work and back everyday and hit the dirt less than i'd like every other month or so in the desert or Baja. I live in San diego so the the temps are pretty warm. Should I dump the 20/50 and go with a lighter Castrol Actevo oil or stick with it? Why does the pump buzz? I have parked it until I get some info.