Motorcycle Engines Parts for Yamaha YSR50
Produced between 1987 and 1992, The Yamaha YSR50 is a miniaturized version of a race bike. It features an air-cooled, two-stroke 49.3-cc engine and has a top speed of 38 miles per hour. Though miniature in size, the YSR50 doesn't fall under the "pocket" bike category.
How do you make a YSR50 street legal?Most motorized vehicles and motorcycles can be made street legal if they have the correct signal indicator lights, brake lights, headlights, license plate holder, and safety equipment required by state law. One of the biggest issues about making the Yamaha YSR50 legal for street use is the fact that it has a two-stroke, which is loud and fails to meet emission regulations in some states, such as California. From 1979 to the present, any motorcycle 50-cc and under isn't federally regulated. Nevertheless, much stricter states such as California still ban such motorized bikes from being operated anywhere.
Due to these state and local regulations, many owners of a Yamaha YSR50 swap the factory two-stroke for various types of four-stroke motors. Anything from another 50-cc machine to a YZ400F four-stroke MX motor has been fitted to the Yamaha YSR50.
What are the differences between two-stroke and four-stroke engines?The biggest difference between a two-stroke and a four-stroke is that two-strokes have no dedicated lubrication system. The YSR50 motor is lubricated by mixing the oil with the fuel much like what is done with a chainsaw. This means the oil is burned upon combustion as a part of the air/fuel mixture, which is also why some states have stiff regulations on such motorcycles.
What is a top end rebuild?When your YSR50 starts to lose power, it might be because the piston and rings aren't forming a tight seal in the cylinder. When this happens, it can scuff and scar the bore, causing the motor to become sluggish. Furthermore, if this problem doesn't get fixed in a timely manner, it can cause a weakened piston to crack from the pressure. A top end rebuild is when you replace the piston and rings and possibly rebore the cylinder in your two-stroke.
Mechanics who work on two-strokes suggest rebuilding the top end of the motor periodically since such projects are relatively affordable and will prevent worse damage from happening later on down the road. There is no set time frame between builds, as each owner runs their YSR50 differently. If you simply like to cruise around, these types of builds can wait for years. On the other hand, if you like to race your Yamaha YSR50, you may be required to rebuild the top end more frequently.