I had the clutch in pieces of a similar 50 cc engine last night.
The clutch housing looks like a small straight-sided bowl. Inside there are three clutch plates. Two have fibre on only one side and one has it on both.
The only difficulty was me trying to get the clutch assembly off using a hammer and chisel. I don't have the correct four-pronged-tool for it. But I managed to get it off and fixing the gubbins doesn't look very difficult.
There were eight + screws on the exposed side of the housing. Four were there to keep a cover on the middle and were recessed. The other four were round-headed.
I could easily remove the recessed ones but the round-headed ones were obviously going to be rounded where the screwdriver fits in. I used vice-grips to start the screws turning. Would the correct tool for that be an impact-driver? I'm sure any screwdriver would have just rounded the insides. - But then I could have used a hammer on the end of the screwdriver and twist, but it was too late at night for that.
I am hoping the 50 cc engine's clutch is the same as the 90. We shall see.
The engine I used to test how to get the clutch off was seized. But that was only because it had been outside in the rain and the piston rings had rusted to the cylinder bore. And the coils had stuck to the flywheel.
so I filled the spark plug hole with CRC and used a rubber hammer and a chisel on the timing mark on the flywheel to nurse it around a stroke or two.
But the flywheel was pretty gritty so I decided to take it off to clear the bits out. Of course I don't have the correct tool, but I have got a pulley-puller, which after a bit of violence was fitted satisfactorily.
It didn't want to come off and it was four o'clock in the morning and I thought if it suddenly flew off as it was under a lot of tension it would be pretty noisy. So I was just about to slacken the puller and get some sleep when it decided to pop off and knock some tools off the bench and the flywheel itself ended in a stack of wood, which also fell over.
It's amazing what you can accomplish with violence and pig-ignorance, isn't it.