[Barnsnake]

The engine would start fine at 6 degrees.

Before you throw any money at the problem make sure you're addressing the right problem. My engine didn't want to turn over when it was hot. After changing the battery and increasing the cable size (with no significant improvement) I decided I needed to back off my initial timing and change my advance curve. Just before I started making the changes I decided to check one last thing. I got the engine good and hot, let it sit for 5 minutes, pulled the coil wire and grounded it. I then tried to crank the engine. It still cranked like it was trying to run backwards. I installed a high torque starter and it has started like a champ ever since.

If you have high compression and winter fuel, it's entirely possible a spark retard is the right answer. Just try the test above one time to be sure.

Let us know what fixes it.