In What Year Were Dirt Bikes Invented?

Dirt bikes are basically off road bikes which are very light in weight and the engine is small. The wheels of dirt bikes are large in diameter when compared to other tyres of bikes and moped. The body is constructed in such a way that it is always suspended at a greater level from the ground with the help of large knobby tyres. They are mostly used for motor sports like moto cross. In this kind of sport the bikes have to race over jumps. These bikes are generally light in weight and their capacity varies from 125cc to 500cc and also has a good suspension with high endurance and has 2 or 4 strokes engine.
     
Some bikes are built on specifications related to the motor sport like Trials. This is where speed doesn't count and bikes are built in such a way that main priorities are given to precision and balancing skills. The first dirt bike was invented by Kawasaki.

KLR650 was the first dual purpose dirt bike which was invented in the year 1987 and this model remained unchanged until 2007.

I think you have to go back way longer than that. I know of dirt bikes dating back to the early 70's, I remember an old Husquarna 250 I've seen from around that vintage and I suspect it goes back further than that as I doubt I saw bike no. 1 so my guess would be we are in the 60's.