1.5 years hibernation is nothing. Please do the following:
1. Wash the Avenger and clean it thoroughly.
2. Change the engine oil, gearbox oil, clutch oil, front brake oil, air filter, engine oil filter, and front suspension oil.
3. Adjust, clean and lubricate the drive chain.
4. Fill up the tyres to the correct air pressure.
5. Lubricate the throttle, brake, and clutch cables/pedals, side stand. Change any cables that are frayed.
6. Get a new battery (Rs. 1600).
7. Check the wheel spokes (front and rear) - tighten them if they are loose.
8. Check the functioning of all bulbs and replace if necessary.
9. Clean/replace the spark plug (Rs.80).
10. The clutch would be sticky due to non use - pull the clutch and roll the Avenger for some distance to free up the clutch before you crank the motorcycle.
That's it, you're good to go. Ride the Avenger and feel like God