Actually, using a small rear sprocket makes starting EASIER by far!
When my bike had the stock 44 t it was a PITA to cold start! After changing to the 36, it is a breeze, even if it doesn't fire right away or I need to choke it some, I can keep pedaling, or usually just pedal and coast and it will start.
With a 44t cog, the wheel turns the motor more rotations per turn of the tire, than with a smaller cog. Perhaps changing to a 40 or 36 will help you with your starting problem. Also, making sure everything is properly lubricated (chain, engine bevel gears, and wheel hubs) will help.
Originally Posted by killercanuck
Like mapbike said, you could add another head gasket if it gets too hard to start again. You must be running a small rear sprocket.