1. Make sure the piston is on TDC.
i. From the marking on the flywheel.
ii. From the fuel cam.
iii. Push rod should be free. (both the valve should be close at this stage ie at the end of compression stroke)
2. Make sure the engine has cooled down.
3. Loosen the lock nut of the rocker arm.
4. Now adjust the tappet clearance between the rocker arm and valve stem by tightening or loosing the nut below the lock nut.
5. Use feeler gauge to adjust the suction valve clearance as .35mm an exhaust valve clearance as .45mm