The TRX 90 has what is called a top gear limiter switch. It really does not have a rev limiter per say. The top gear limiter switch only works when the quad is shifted into 4th gear. Often times you will find that the bike will go faster in 3rd than it will in fourth this is because the engine is allowed to rev to its full potential in every gear except 4th. To remove the limiter find the pink wire going into the cdi box and cut it. That will bypass the top gear limiter switch.