Two recipes for better acceleration.
a)Weight loss. Sometimes it's not easy to remove pounds and still keep it streetable, but it will seem like you've already increased torque without touching the engine. You already have a 4-1, which may or may not help power output but should weigh less than original.
b)Power increase. You've already got good info on where to search here for advice. An increase in compression, even some mild porting with a cam and better valve springs gives a nice bump and won't affect reliability.
Regarding suspension and handling mods, these bikes are quite good anyway, but....
tapered roller bearings in the steering head,
replace wheel bearings,
redo swingarm bushings with brass and replace the original collar. (check with Hondaman here)
disassemble and clean forks. Replace old springs with progressive fork springs and or look at installing emulators.
make sure your wheels are straight & true and spokes tight
good shocks, there are still lots of good ones available for these bikes.
