SIr the only good engine is that is bolt on swap and do not waste your time and money on workshops after the swap.
Aap ki gari bhi 23 years old hai tu engine mein kiya masla hai.
Just kidding, you can not state an engine old that has an aluminum block and 12V with 9:3 compression ratio.
I have the same Accord, still with me, the A16 is a square engine, can touch 190 km/hr, has more torque than a 1.3L iVteC engine at nearly half the RPM and I have measured 11.5 km/l two way average with family and luggage on a trip to Hyderabad, you can even drive the car in 3rd gear from stand still.
The only difference is that my engine only has 97K on the meter.
@Xulfiqar bhai has given you the best suggestion, rebuilt the engine.
I can assure you that apart from him, there are not many people how can even think to fit the D series, F series or B series (Civic one with short stroke) engine, I have tried it once on a friend's car and even I have the 400 pages working manual of the car, it was not proved to be successful.
Check the compression test, clean and service the jets carb, adjust valve clearance when the engine is cold, change the spark plugs to Denso W20EXR U series, check/replace the spark plugs wires and do the Big 3 for grounds, service the distributor and ignition and adjust the timings to +- 20BTDC, I will confirm that after reading the owner's manual.
Also check the clutch and pressure plate for proper transfer of power to ground.
You can also upgrade to the bigger twin barrel or electronic carb from weber or Samurai, if you can find one in the Junk.
Afterwards, can also get a sports flywheel.
Lastly you can change the rings and pistons for 10-19K depending on quality and your engine will be as good as new.
Replacing the engine will lessen your car's value by 50K Rs straight and you also have to update your excise registration.
Nothing runs better and trouble free on CNG than this engine, that I can assure you.