After 3 years in storage, there is probably some corosion inside the engine.
I'd start by changing the oil. Use some high quality oil, a cheap one just won't do. If you use a cheap oil, you should change it for a good one after 1 or 2 weeks.
Next, pour a SMALL amount of oil in the cylinder(s) and manualy turn the motor for a few rotations. This will coat the cylinder(s) with a layer of oil. It will also remove some rust.
Open the cylinder head to expose the cam shafts and valves. Make sure that everything is shiny and coated with oil. Check that any rocker is free to move. Make sure that the valves can smoothly slide up and down.
Check that the valve springs are all intact. Replace any damaged element.
Kuälinar, December 2011
