$1800 for a top end rebuild sounds really high to me. I can see $600 in labor but not $1200 in parts.
A top end "kit" from Wiseco, including piston, rings and gaskets should be around $150. You might need the top bearing for another $15. I am not familair with the cost of having a cylinder re-plated but I can't believe that it would be more than $200.
If you aren't willing to do this kind of work yourself, you should never have bought a bike that wasn't running!
Use this as an educational experience. Rebuild the top end yourself, it isn't that hard. It is a different story if you have to rebuild the bottom end but top end can be done with basic tools and a few hours of work. You don't need to remove the engine from the bike.
You will probably want to remove the gas tank. I am not familiar with your bike but I would expect that you would remove the cylinder head (four to six nuts, radiator hose), remove the pipe, remove the cylinder base nuts (four) pull the cylinder off, remove the piston from the rod. Stuff clean rags into the case opening to keep junk out.
I am not sure I would use the shop that quoted you $1200 in parts but I would find a local shop to work through to have the cylinder plated. Have the cylinder work done first to make sure of the size as it might come back bored out to a larger size (oversized pistons are common).
The one "gotcha" on reassembly is to make sure that the ring(s) has proper end gap before you assemble. To check end gap, insert the ring, by itself into the cylinder. Use feeler gauge to check the gap. If it is too tigh, file the end of the ring down a bit.
Put the ring on the piston (be sure the gap is in the right spot, usually away from the exhaust port). There may be only one spot on the piston that it fits properly due to a "tab" in the ring groove that fits in the notch of the ring at the gap.
Put the new piston on the rod, being very careful to seat the spring clip properly (lots of rebuild failures are due to the spring clip coming loose....)
Put the gasket in place, slide the cylinder down over the piston. Tighten the base nuts (toque wrench should be used).
Put the cylinder head in place (with gasket/O-ring) tighten head nuts. Torque wrench is essential here! Tightening the nuts in the proper order is also essential.
Reconnect the pipe, radiator hose, install gas tank, go ride! (go easy at first).
Obtaining a manual for the bike will fill in the blanks, such as the proper torque settings. The after market maunals, such as Clymer, are fine.
Rod
