Need help with freestyle, won't start

May want to be more descriptive. Are you saying it won't fire at all or it only runs when pull starting?
I'm assuming it turns over and just doesn't light off.
Check for spark first. Pull plug/wire and ground out the plug. Try to start, see if plug has spark.
If not, possible problems, loose plug wire or cap. Kill switch or tether switch off. Short in wiring from kill switches.
If has spark then must not have fuel. Plugs not getting wet?
Not sure there, if they are efi or carb.

You said the battery was melted near the positive terminal...That is near the exhaust can. We completely melted the battery and side panel because the sled was running so lean that it heated the pipe enough to melt everything around it. Luckily the engine was unharmed. You should check your cylinder and also check to see what jetting is being run.