Assuming you have a 2 stroke moped with an exposed cylinder head... then scraping carbon off the head is as easy as pie (cake?).
And you could only screw it up if you strip the head bolts when you go to put it back on or something like that.
As long as you do not use a pneumatic jackhammer or dynamite to get the carbon off.. you really can't go wrong.
However... there is no performance improvement to be had by scraping carbon off the cyl head.. in fact it will reduce your compression.. which means less torque for acceleration.
There is one possible problem though... if you attempt to scrape the carbon off the top off the piston without removing the cylinder you will undoubtedly leave some loose carbon bits down around the piston rings.. which can't be good.. (and again.. there is no performance gain from this either).
If.. however.. your exhaust port is clogged with carbon.. then you WILL get more top end.. you can check this by laying the ped over on its side and removing the exhaust pipe and looking up at the piston.
To clean that out properly you will need to remove the entire head and cylinder and scrape it out with a screwdriver or whatever... scratches won't hurt anything.
nitey nite yall