3 months travelling Central America (x-post from r/backpacking) tips? advice?

So I'm from the UK, I plan to fly to Guatemala in april, and then travel down to Panama over 3 months. What I loved about travelling the last time I went was the times I rented a bike and explored with pretty much complete freedom. So I plan to buy a quadbike (ATV), motorbike or even a car and ride/drive the entire distance. I have relative proficiency in quadbike and motorbike riding, and I can't foresee any serious issue with driving out there. Any tips on travelling solo out there, which vehicle should I buy and how do I go about buying it. Oh, I'm 20, male, learning spanish and will be travelling solo.