well the 1st thing u did was to get rid of the cng kit....
now you need a nice tuning job which includes plug wires , plugs , a clean carb, feul pump.
need to evaluate the condition of the engine
keep r12 rims with 155 radials
If you have a 5 speed gearbox , that would be an advantage else keep it on low rev and slow cruising, no need to be a speed demon
try keeping the tank full and refill every time the mark hits 1/4 remaining
avoid high traffic areas and maintain a decent speed on high gears
The machine which you purchased is a well built daily runner and will go a long way with periodic maintainence
good luck