Removing and reinstalling the cylinder head on a Chang Fa or any other small engine with 4 head studs I came to the conclusion that there may be hidden traps hidden in these simple engines like reinstalling the head. " Ok I have a gasket and torque wrench I am set." Maybe? There is not a lot to write but we need to understand how the head gasket works ( I will Ad photos at a latter date ) There is in the center of the gasket a crush ring or compression ring often made of copper it can be flat or round but this ring seals the compression and combustion presser in the cylinder. The flat surface of the head seals between the crush ring ( shown in orange ) and the liner top ( shown in red ). This is finger tight on the head bolts the head is sitting on the crush ring of the gasket and not on the black areas shown right and blue area shown left ) This is a point you should push the head down on to the gasket as flat as possible and take the cap screws or nuts in the case of studs down finger tight till they all touch evenly now the head is sitting square on the gasket. crush ring and is a 1/1000 th or so off the black area. We must torque the head bolts evenly. The most accurate way to do this would be to torque each bolt by degrees ( in a crisscross pattern in small increments ) until we crush the ring between the head and the liner top till we now compress the coolant sealing area (shown in black) for a few thousands. If the coolant surface is dirty or old gasket material is left it can tip the head a bit. Since we are only dealing with a few 1/1000s this can lead to leaks. Unflatness of the head or the deck ( shone green left ) can result in water leaks these surfaces should be checked if there is a question or an on going water leak. If of the head bolts are torqued unevenly ie down on one side the head can be tipped causing a water leak . The crush ring can take a fair bit of tip and still seal compression , however the coolant sealing area can not be tipped much and still seal properly
The morel of the story is:
1: Push the head on with the gasket and turn bolts/nuts down finger tight till they contact the head
2: Torque the head bolts in a crisscross pattern in 10 foot pound increments .