What's the most underrated upgrade you've done on your mini bike?

I've been going through my build log lately and noticed most of us talk about big bore kits, exhaust, and carn swaps. Those are fun, but I think a lot od smaller, cheaper upgrades get overlooked.

For me, it was upgrading the rear suspension and swapping in better quality bearings all around. The difference in how it handles rough trails and holds speed through corners was night and day. It didn't add horsepower, but it made the bike way more usable and less tiring to ride.