definitely sounds like a speed sensor issue - aka revolution sensor.
cant tell you exactly where its located but it should be replaceable - by a good competent technician.
purchasing it. if you can get the part # you can order it yourself from the US or japan...or you can try massey motors
i'd recommend you consult with this guy. ryan ramdeen aka ryotech performance
see link >>
viewtopic.php?f=6&t=418527he may be able to assist you.
