This is a short and sweet guide on how to speedrun the full championship category (the longest of them all). This category, like the others ones it isn't too difficult to learn nor practice. All you have to do is to speed through all championships and reach the end. Hopefully this guide can help you get a decent time and make you want to come back to do new attempts. This guide is mainly focused on the PC version of the game although the PS1 version should be the same.
Alright let's begin.
The first Championship you start off with is the Super Bike Championship. It's the easiest of the bunch IMO and you should power through this one with ease. It's only the motorcycle portion and if this is your strong side then go all out. My recommendation is to go for the light blue or the orange bike for maximum speed and acceleration. However, it's up you to choose which bike suits you the best and your playstyle. The bike with the slowest acceleration is obviously not recommended as it takes too long to get up to speed. Doing wheelies is strongly recommended because you hit max speed more often and hold a steady lead. It's wise not to do wheelies before corners or in a group of other bikes to avoid crashing.
Second championship is the Moto X championship. Only motocross is throughout this race and it's important that you focus on not hitting the edges of the track. If you fall off the bike then that will lose a lot of time. It's way easier to fail on a motocross than a motorcycle. The key to gain speed is constantly doing wheelies, but be warned! Other bikes will always be around you and it's a big risk that you'll drive into them by accident. If you're experienced then it's recommended that you do sharp turns and stick to the inside corners. That will help you gain time and keep your momentum.
Third championship is a mixed bag. Both motorcycle and motocross races take place here. The choice of bikes should be light blue or orange for both modes. Note that it is my opinion and you might come up with a better combo than what I'm describing here. Try to speed through the menus as fast as you can since you're selecting bikes quite often.
Fourth and final championship. This is just like the previous championship you just did. It contains mixed vehicles and has somewhat long/difficult courses. Make sure to practice these courses beforehand and get a good understanding of all turns/twists. Practicing motocross would be my recommendation since it takes more skill than driving motorcycles.
Now, if you manage to crash very little you might end up in the 1h 30m region. That is a very good time and that's where the current WR stands. I'm not sure about the potential of this record but I would say you can get a really good time if you speed through menus and drive flawlessly.
This should secure a nice victory. Thank you for reading this guide and I wish you the best of luck! /HolyFists