I did a 1/2 day ride north this morning and noticed a lot of motorbikes out but most of them were parked at coffee shops with riders holding steaming mugs with both hands, crouched over, trying to get warm.
Looking at all the expensive motorcycles I am guessing it is not lack of money that stops people from having proper winter gear but their desire to dress a certain way, to project a particular image.
So here is a few ways to warm yourself up if you simply have to always wear your draggin jeans and leather jacket.
1. Buff/Scarf. Stop the wind getting in around the top of your jacket. Essential.
2. Windproof mid layer. A fleecy top will not really do much once you are moving wearing a leather jacket, get something to stop the wind. Outdoor shops sell these but often made for hiking so not really windproof. Better to buy a item made for motorcycle riding but again check it is totally windproof including any zipper.
3. Glove liners. In winter on cold mornings pop a pair of glove liners on under your gloves and be amazed at the difference. When it warms up simply roll up and put in your pocket.
4. Thermal lowers. There is a number of motorcycle branded thermal under garments on sale but get ones that insulate from the wind and still regulate temperatures. Spidi for example make some where as non windproof items will not be effective.
5. Get a pair of good winter riding socks. There is a real difference, seriously. I use the Alpinestar boot socks and they wick away moisture and keep my feet warm but never hot and sweaty.
If your not wearing boots then keeping lower legs and feet warm will be very difficult. Give some consideration, they are great in summer too as stop the heat from engine or exhaust on lower legs.
Of course you could just buy a full winter riding gear but if you think it is something you will not get the use out of then perhaps these ideas may ease the chill on your next ride.