1991 Polaris 4x4 trail boss good condition new to me about 5 months ago, some times it starts easy even in the cold but other times its a pig and will not start in the cold or when its warm, it has new plugs, good gas, new air filter, engine liquids have been changed Polaris two stroke oil is being used.
If you need more information just ask and I will post it.
Thank you

 

Test the battery voltage. If it is low, it can cause erratic spark voltage.

If it is hard to start after sitting for a while, but starts OK if you ran it recently, that is kind of normal.