Maverick,

You should do a compression test. This is done by pumping compressed air in each cyl. and getting the pressure reading. This can be done by any shop with the right equipment.

Pump air thru the spark plug hole when on TDC.

You will know where the culprit is when you hear the hissing sound from....

1. Intake (carb or air filter)....leak on intake valve.

2. Exhaust (tambutso)...leak on exhaust valve.

3. Open oil cap......leak on piston rings.

4. Try also to check hissing sound sa radiator....water jacket/gasket

The pressure reading should be the same for all cyl. and should be 85 - 90% of what you put in. Kung may piston na mababa, yun na ang culprit.

By this malalaman mo kung valves, piston rings or gasket....

my 2cent