I have a 4 year old XT-1. with the 25h.p Kohler. it has spells of not wanting to start. when I turn the key i get a high pitched whine & when it tries to crank it kicks back kinda like on an older car that timing is too advanced. connections are clean & tight & the voltage meter reads 12.5 volts when the tractor is off & 13.5 while running. the battery is new. i'm thinking about pulling the starter & having a look inside, might it be a bad bar on the commutator?