First Timer w/ Apollo 250

[603Dirt]

Hi guys,

27 y/o from southern NH here. I haven't been on a dirt bike consistently in over 10 years and wanted to get back in the dirt and eventually on the road after gaining some experience. I know how to turn a wrench and perform basic maintenance and and I'm interested in learning as much as I can.

I purchased a 2017 Apollo 250 with roughly 10 hours on it (or so the previous owner says) for cheap money on Craigslist a few weeks back. I've been on this forum a few times and look forward to posting and interacting with you all.

Since I got the bike, I've taken the stickers off and cleaned the plastics, fussed around with the air filter (what a pain in the ass!) and plan on changing the fluids and maybe the carb if necessary. The previous owner replaced the OG battery with a 12V EverStart AGM Power Sport (Walmart brand) dry cell battery with two pieces of OSB stacked next to it to keep it in position!

What I've started working on:
-I can hear the electric start click when I press it but it has not worked. It starts right up with a few kicks but idles rough unless you hammer on it. I suspect that the battery might be playing a role with the electric start and that the old gas and OG carb might be causing the rough idle but welcome any suggestions.
-I've seen a Youtube video on changing the oil on one of these 250's and they recommended cleaning the filter with brake fluid and then reusing it. I'm leaning towards just purchasing a replacement filter depending on its condition and was hoping you guys could provide me a resource to purchase one.