2000 Polaris sportsman issue please help!!

I’m new to the forum and also new to owning an ATV. I was given a 2000 Polaris sportsman 500. There are a few issues with it that I’m hoping to get figured out. When I got it i had to pull start it since the battery was dead. It was a new battery I was told but it seems to not stay charged. I rode around for 10-20 minutes and it overheated, the fan didn’t come on. So I decided to go get a new battery first. Replaced the battery, fan came on as it should and it didn’t over heat and I rode around for a good hour. An hour later I came back out to ride around again and the battery was dead! Pull started it rode around for a short time, fan wasn’t coming on…overheated. Something somewhere is draining the battery. Why does it keep doing this. I’m somewhat good with fixing stuff but by no means a mechanic. Hoping someone could give me some opinions.

I was thinking the fan should come on when it’s running regardless of the battery?? I’d imagine there’s a sensor somewhere that tells it when to come on but why does it only work with a new battery. I figured if I pull started it and it is running then the fan would work. Like I said I’m no mechanic so any help is greatly appreciated!

2000 Polaris sportsman issue please help!!

I’m new to the forum and also new to owning an ATV. I was given a 2000 Polaris sportsman 500. There are a few issues with it that I’m hoping to get figured out. When I got it i had to pull start it since the battery was dead. It was a new battery I was told but it seems to not stay charged. I rode around for 10-20 minutes and it overheated, the fan didn’t come on. So I decided to go get a new battery first. Replaced the battery, fan came on as it should and it didn’t over heat and I rode around for a good hour. An hour later I came back out to ride around again and the battery was dead! Pull started it rode around for a short time, fan wasn’t coming on…overheated. Something somewhere is draining the battery. Why does it keep doing this. I’m somewhat good with fixing stuff but by no means a mechanic. Hoping someone could give me some opinions.

I was thinking the fan should come on when it’s running regardless of the battery?? I’d imagine there’s a sensor somewhere that tells it when to come on but why does it only work with a new battery. I figured if I pull started it and it is running then the fan would work. Like I said I’m no mechanic so any help is greatly appreciated!