I have a 2001 KE100 that I bought last year. I already had to fix the carburetor and replace the tranny oil. I used Yamalube 10W-40 All Purpose Performance. The manual calls for 10W-30 or 10W-40 Grades: API SE, SF or SG. The guy at the store said this would work. Would this effect the gears after the clutch is released or could it be something else?