I did a ride today, was 50 degrees and decided to try the following combo, worked great.
1. Base layer - smart wool long sleeve 200 weight shirt
2. Insulation layer - down "sweater" fall weight jacket.
3. leather jacket
The down sweater was new for my ride, I've had it for hiking and casual use, first time on the motorcycle. did not feel bulky at all, fluffed up where it could and compress where tight and very light.
Something like below.
http://www.amazon.com/Mountain-Hardwear-...B00A8OF74C