i have a 2002 polaris magnum 325 2x4, but for some reason its been to bogging down and power isnt what it used to since couple months ago, when i give it gas it makes a voovoomvoomvooomm noise then it goes normal when just going a normal speed. it also feels like the power isnt what is used to, Today we changed the oil and put a brand new oil filter. the oil is "diablo maxima oil 250cc" even though its a 325 but dont think it really matters, its still feel the same powerless bogging. Also when i drive a lot in hot tempertatures or just going trail riding i never ever hear the fan. or who knows if its a really quiet fan but i never hear it. it seems that it is connected but it doesnt seem to turn on. any help?