Welcome to the wonderful world of the china girl engines!
Cheesy, poorly cast aluminum parts a specialty!
#1, Are you talking about the long head stud bolts that thread into the crank cases?
#2, the stock fiber exhaust gaskets and exhaust spigot sometimes leak, dont sweat it, we can fix that easy.
#3, Is the case cracked were the head stud threads into it?
If it is cracked, it can be welded up, re drilled and tapped.
Its a pain in the butt but it will save the cases
If its not cracked your in luck, a Heli coil insert is your best bet to repair the crank cases with out to much drama.
Ok now to the original problem, the exhaust leak.
2 strokes are very sensitive to any exhaust problems so this parts important,
#1- Once the cases are fixed you'll need a new cylinder base gasket and an old school product called Gaskacinch gasket sealant or a similar product, with the mating surfaces of both the cases and cylinder surgically clean and totally free of any trace of the old gasket(i use acetone for this) brush a THIN coat of the gasket sealer on the gasket its self and hang it up to dry over night, it will still be sticky to the touch.
#2- Lay the base gasket over your fresh head studs and slide the cylinder CAREFULLY over the studs.
#3- The Cylinder head/cylinder barrel interface is designed to work with a metal head gasket and NO sealer, lay the new head gasket in place CAREFULLY over the studs.
#4- now lay the cylinder head over the studs, make sure everything is lined up correctly and add the big washers and hand tighten the head nuts as tight as possible.
#5- using a criss cross tightening pattern step up to the indicated torque value incremental, a little bit at a time until you arrive at the right torque value.
Congratulations, you just did a partial rebuild of your china girls top end... feels good dont it?
Ok, now for that exhaust spigot and gasket
I use the thick aluminum exhaust gaskets available from several suppliers, they just plain old seal better.
#1- clean off the exhaust port mating surface of any remains of the old gasket, make sure its perfectly flat.
#2- look at the mating surface of the exhaust spigot, is it welded properly? put it on a flat surface and see is its warped or bent, if it is it will rock, this causes 90% of exhaust leaks.
Depending on how bad the warpage is you might need a new one, if its not to bad you can fix it.
#3- put the spigot in a vise mating surface up, make sure its sitting straight in the vise, then useing a large flat file, file it flat, keep standing it on your flat surface till it doesnt rock any more, then use a sanding block and fine sand paper to smooth the mateing surface.
#4- lay on the new exhaust gasket clean, no sealer, exhaust port studs should be fully seated in the cylinder port holes, install the spigot over the gasket and studs then lay on the large washers to evenly distribute the torque and keep t from warping agian as its tightened down, TIGHTEN EACH SIDE A LITTLE AT A TIME!
You just finished tweaking and installing a exhaust spigot.
Good luck, feel free to ask questions...
BBB