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I had the same problem, and mine was that my solinoid was sticking in the cold weather. I replaced my whole starter.
I bought a starter from Terry @ Sentry South
(Scroll to Bottom of the Page), and then after working on it for a few hours, brought it to my mechanic to have him replace it.
Read About it here There is a good chance that it's not your flywheel (You better hope that it's not), but the weather is just too damn cold to work on it yourself without a heated garage!
