Price depends on how much damadge was done when it overheated.Mechanics are pretty expensive.I'd say around $1200.00 parts and labor top end.If you need to split the cases,then closer to $2000.00 parts and labor.

I also believe that a motor is as reliable as you treat it.High compression motors dont last as long and are expensive to run.They are fun to have though,especially when the competition is breathing your dust.

I like to up the bore and compression just a little in my YFZ.A good port and polish with a carb bore is also a good way to make it run sweet.