The reason AMA supercross went from 2 stroke to 4 stroke race bikes

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AMA super cross has been around for a very long time. Since the early 1970s when the first race was in the super bowl and it was called super bowl motocross but then came the term and the start of supercross. In supercross these were tight cornering tracks with big jumps rhythm sections, and woops sections. The bikes that were first ever ran on these tracks were 2 stroke meaning they are high rpm bikes which of the time were the fastest bikes around of this time but there were a lot of issues with the bike which I will explain. Supercross has changed over time the bikes the tracks and the pace of the race.

To start off with some facts and information on a official 2stroke 125cc and 250cc race bike. The 2stroke dirt bike is a bike where the motor runs of a gas and oil mix where the gas and oil are mixed together in the gas tank. The dirt bike is also cooled by a radiator and coolant in the radiator. The coolant being antifreeze. The 2 stroke motor is a 2 cycle engine which means every 2 cycle of the engine there is 1 power stroke. The 2 stroke has a cylinder in which It has a two holes in the bottom of the cylinder when the piston comes down and the holes are opened the gases that were just burnt and exploded are pushed out of one hole by new air and new gases coming in through the other whole. Then the piston goes back up and closes the holes then compresses the air and the gas together then there is a spark from the sparkplug igniting the fuel and air mixer pushing the piston back down and restarting the cycle. Now this happened at and unbelievable rate. At 12,000 rpms the motor is spinning at 200 revolutions a second. So the motor is doing 200 of the cycles that I described to you above in 1 second. This ...

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...e fuel and air and then again the sparkplug provides a spark igniting the mixer creating the power stroke sending the piston back down restarting the cycle. This engine has a lot more compression and just takes straight gas and air. With a the oil being completely separated from the gas. This engine was a lot more reliable because it didn’t spin as fast and never got as hot it lasted a lot longer and barely ever need rebuilt. Just maintain like new oil, coolant, and a new spark plug was about all it took to keep these bike running and because they weren’t rebuilt between each race the bike would be no different than the one they had raced in the previous race thus keep the rider more comfortable and more in control of the power of the bike. This lead to faster lap times more safe bikes and in the end a whole new style of racing for the world of Supercross.

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