Q: I recently purchased a 1986 GSX R750G. It is a Jap import, but I have read in your magazine that these bike are restricted to 75bhp and it certainly does not feel as quick as it should be, Where are the restrictions in this bike and how can it be derestricted back to its natural 100bhp?
A: There is quite a bit of debate on this subject but as far as I can glean, the restriction is based around two things. The speed has been limited to 180kph (i.e. the limit of the markings on the Japanese market speedometer) and this is done electrically at the speedometer. You might need to check your wiring against a wiring diagram for the UK specification model to see what differences there are and try cutting any extra wires as an experiment. The other restriction is by limiting the diameter of the exhaust pipes near the exhaust ports, and these can be ground out to more suitable dimensions.Enjoy more Classic Motorcycle Mechanics reading in the monthly magazine. Click here to subscribe.