My 99 Sportsman 500 alway's cranks over hard (just like a car when timing is too far advanced) and won't start only when below say 20 degrees. Former owner stated he replaced starter and solenoid and it never cured it. When I jump the solenoid it starts up. Usually if It doesn't start I put the charger on it for a little bit, then it to will start fine. Starts great and normal all year long until it gets EXTRA cold out. Then this symptom occurs. Just replaced the battery 3 months
ago. Could it be in the handle bar switch? Thanks for any help.

 

Make sure first all connections are tight,battery solenoid,etc. Do you keep it on a battery tender? May help if you don't. Sometimes even if you do have on a tender cold weather can suck em down same as hot weather can.Faster than what a tender can even keep up with. Amperage along with voltage can drop pretty quick. If you have a volt meter hook it to the battery while you try to crank. If the voltage drops past 9 volts while tying to start,the battery may not be as good as you think.