hey im fixin up my 83 xl 600 and am trying to solve the problem of not getting enough oil to the head. (i just had to replace rockers and cam) i driilled out the banjo bolts and ive heard some people use thinner oil. im using 10w40 now and am thinking of trying 5w30. will this have any major negative effects on my engine? or should i use 10w30 and switch to 5w30 in winter?