DesertRat wrote on 12/10/15 at 04:30:40:Dave - I haven't re-jetted yet, still stock. No choke, she won't even turn over with the choke out!
What does "turn over" mean to you? Does that mean the starter turns the engine over - but the engine will not start? Using the terms "won't turn over", "won't crank", etc. can be very confusing. If the starter turns the engine over - but the engine won't fire or won't start....that may be a better description for what is happening for you.
I do believe the Rotella is 15W-40....I don't think Rotella comes in a 20W-50. The oil could be too thick of oil for 30-50 degree riding. It could be that the starter is working too hard to turn the engine over and either there is not enough voltage left over to supply the ignition system adequate voltage - or the engine is rotating too slow to get a good vacuum in the carb to pull adequate fuel into the cylinder. You might try a thinner oil....I am not familiar with what 10W-40 oils are suitable for the Savage and has adequate ZDDP and is safe for the wet clutch.
However...that does not have any affect on the backfiring once the engine is running. If "stock" means you still have a #47.5 pilot jet, I would consider a #50 or #52.5 as a cold weather option.