its running weak mate,take the caburettor off and take all the jets out and make sure they are all clear through them,make sure the air filter is fitted properly and has no leaks in the piping or air box lid.if it persists then take the needle out of the throttle slide in the carb and take the small circlip off and move it to the groove nearest the pointed end of the needle.
adam bike doctor, July 2010
