I have one that my daughter rides that is a 1987. I wouldn't call it modded, more of a tuneup. Those things are setup VERY conservative from the factory. All I did was advance the timing a few degrees, drop the main jet one size, new sparkplug, and make sure the clutches were in top shape. I also made sure the rest of the chasis (bearings and all) were in good shape for low drag and rolling resistance. With my son piloting, it pulled 54 mph according to the speedo on my 09 Phazer RTX. That speed was the subject of some controversy last winter when I reported it on this site. Some believed that there was no way a 250 single would run that speed. Regardless, I feel that it is plenty fast for my 8 yr old daughter for trail riding. It even pulls decent with my 220 lbs on it.
If ur really serious about making a Bravo fly, I would consider swapping the 250 single for a 300 or 340 twin. Don't think there are to many aftermarket parts out there for Bravos. Would most likely have to fab ur own.
I saw 73 mph on the speedo on my old 78 250 enticer when I was a kid and about 85 pounds. That was on perfect snow packed road long run and I thing it was closer to 65 real speed.