Don't have a "how-to" compiled, but here is a link to some exploded parts views that might help you gain some insight on the process. In a nutshell, you remove both side covers and everything externally located on the crankshaft to gain access. Here's some PN's for things you may need for your project, 810790(1) Top End Kit, 650107(4) Flange Nuts, 650112(1) LH Seal, 650113(1) RH Seal, 650651(4) head studs, and depending on how it comes apart, you may want left and right cover gaskets. Eton America - Part Catalog We are an Eton dealer, feel free to send us a PM or a give us a call for any of your parts needs.

 

Remove the shrouds aound the cylinder. Remove the exhaust. Remove the carb and reed cage. Remove the 4 head nuts. Now you can remove the head and pop the cylinder off.
Get yourself the next size piston kit (stock or Pro-X) (prolly a 50.5mm), new piston pin, pin brg, and cir clips, head and base gaskets.
Take the cylinder to a shop that bores and have them bore to the piston.
Assemble.
That's the quick version. LOL

 

do that for replacing the crank seals?

 

OOps...lol
I see you have a fresh top end.
My bad.

 

new crank seals are on the way so we will see.

 

Update: it's running great now, I pulled the intake, reeds great shape, looks as though gaskets where old and brittle, I cleaned the surfaces up and for now I used RTV to make gaskets put back together and now she runs!! Thanks for all the help