A subject close to my heart living where I live.
A good jacket and pants with a fleecy liner helps. Thermal undergarments, best quality you can afford. Kathmandu and other better quality camping stores have sales on where you can get three sets for $60, which sounds expensive but they're worth their weight in mint Z900 parts. Also get a balaclava and a pair of under-gloves. Decent waterproof boots, Explorer socks and frequent stops to warm up every hour or two. The colder you get the worse your reactions become and the more sluggish your brain works.
If you're riding in cold foggy weather a waterproof outer layer is a must, denim just gets waterlogged, which cools you down even quicker even with thermal undergarments. Waterproof gloves for the same reason, cold clammy leather is a PITA. As a bonus some winter gloves come with a wiper blade on the index fingers which is great if you're riding in rain or fog.
Either way you're going to look like the Michelin man, but believe me it's worth it.
You can go the whole hog and look at an electric vest and heated grips.
Mick
