Wow, chain saw also a lot to learn........
Just like car engine but smaller scale.
If cant start check for spark..Most of the time fuel is ok due to design of the carb which does not hold fuel. If no spark then change the coil. If got spark then check fuel supply where it only got fuel screw for idle and high rev.
If chain runs at idle then check clutch. Clutch spring is worn out.
If cant full throttle despite pushing the throttle to the max then check carb linkage.
Always check chain oil level to prevent damage to chain and bar. Its like checking engine oil level on our car engine.
Now got fuel injected saw and battery powered saw.
Best part is change of engine block does not require Puspakom inspection and JPJ approval..hahah