Re: YAMAHA F80 NEEDS HELP
I don't know what differences there are between the Yamaha 80 and 100 but I do know that the hp increase does not come from rejetting the carbs. Carb jetting on any engine 2 or 4 stroke is done to provide the best operational mixture for smooth running, takeoff and idling. Minor jet modifications may occur if it turns out the initial selection was a little too lean or too rich or if fuel grades change over the years. Putting bigger jets in your 80 will make it run rich and you will lose power and fuel mileage.<br /><br />Things that make a 4 stroke get more power revolve around better breathing. Anything that allows the engine to suck in more air or get it out easier and quicker. These would include larger intake and exhaust parts (ie manifold/header, carbs/throttle body, intake and exhaust valves, larger intake and exhaust ports, and increased cam duration and lift. Also modified combustion chamber shape and compression. Many of these modifications simply allow the engine to move the torque band up to a higher rpm which gives more horsepower. Some of these modification, such as combustion chamber design will get you torque and hp at lower rpms.
