@fanno__ So I went to the guy known as Suzuki expert. He checked and assured me that valve clearance is fine. I was thrown away by the fact he didn't have any gauges. But on my way back I bought a feeler gauge and a number 10 socket wrench, myself. This is so I can tweak this sucker myself!
For any one curious here are the tappet clearance settings for GS150.
Intake: 0.03mm to 0.07mm
Exhaust: 0.13mm to 0.18mm
The company provided settings are full of SH*T. DO NOT USE these. It will create loud ticking sound and will of course start damaging the engine.
Use this instead:
Intake & Exhaust : 0.08 mm