i am not sure of the 2003 gsxr 600. but i have an 07' gsxr and i had mine to 171 on the highway in 6th gear.
155mph
174 mph
A standard Suzuki GSXR 600cc has been recorded at just over 170mph.
the top speed of a 2001 suzuki gsxr 1000 is 186 mph
Top speed of a 2007 gsxr 750 is 957 MPH....
The top speed of a stock suzuki gsxr 750 is 180 mph i think it can run faster if you tune it up and modify the engine with racing parts
They are restricted to 186mph in the UK
About 185 m.p.h.
tested speed is 174 mph or 279 kmh
Around 160-170
with a bigger rear sprocket u will be gearing down. therefor u will have better takeoff but lower top speed.