As has alreadt been said, The early model AC had the clear plastic gasket under the sleeve/cylinder assembly. The last model of AC had a o-ring under there only.

If you order as gasket set from central hobbies for an AC, you will get the clear plastic gasket and no o-ring to go under the cylinder.

If you order a gasket set for the 'FZ', then you'll have the o-ring for under the cylinder but the carb gasket may be wrong?

The gasket type crankcase is no longer available.

The regulator diaphragm is not included in the gasket set.

The difference between a late model AC and the FZ are as follows.
The crankshaft/drive washer/key has been changed to no-key. The FZ has a taper lock type front drive washer. Also the FZ has a bigger carb. If you buy a new FZ, it will still say AC on the side of the crankcase.

You need to inquire about your requirements when you call.

Typically, the muffler is what tears up the cylinder head on the AC's. If you purchase a FZ muffler assembly, then the adaptor pipe will break away in a crash rather than tear out the cylinder assembly.

If you heat up the head, you should be able to get the sleeve out. Those sleeves are generally pretty hard, the ones I've seen looked new inside. Heat the head up in the oven on the low setting or warm. Somewhere around 250 degrees F.

When you go to put it back together, generally the airbox gasket presents a problem and if it doesn't then the carb gasket to rotorbox gasket will give trouble. The proceedure is to put the carb/rear rotorbox together and on the motor without the cylinder. Put the box on the cylinder before you put it on the crankcase. Then you set the cylinder assembly down on the crankcase using the o-ring between the airbox and the carb.

These little thin gaskets are delicate and will "suck-in". Then you will have an air leak and you will be chasing your tail for a few days until you figure out the problem. A common problem is that early on a person will realize this and put silicone sealer in the gasket areas. Then first thing you know, there is silicone in the engine or the regulator.

If you take the regulator apart, the *** goes to towards the front. The diaphram has a top and bottom as well as a front.

The idel screw (if you have one, it will be in the center of the throttle shaft on the fuel inlet side) is an airbleed, so it works backwards. Out is leaner and in is richer.

Look up YS engines on Google. There are several sites there devoted to setting up the YS engine. Also central hobbies has a parts exploded view and price breakdown on there.

Good luck,
Jim