I'm 14, just finished my third year of racing karts. 
I started out in "arrive and drive" 5.5hp hondas, Biesse Cadet Chassis. I did that for two years, won the championship both years. 
Last year we ran our own kart, World Formula Jr. 15HP, Briggs 4 Stroke. Finished Third in the Points.  
Next year I might be driving an F1-K Junior. An F1-K is a new class in Ontario, 125cc Maxter engine, CRG Chassis, and it's a spec class. Bit higher top speed then Rotax Junior. 
So far my racing "career" is going great.