PREPARATION : Prepare your work area before beginning. I am a strong proponent of getting and staying organized while performing this type of work, and like to cover my work area with an old bath towel, or even an old bed sheet. A fabric surface helps prevent small parts from disappearing. Gather the necessary tools and supplies for the job—Allen keys, screwdrivers, pliers, a metal-marking scribe, cleaners, brushes, work tray, some shop towels and assembly oil. A heat source such as a propane torch or heat gun is also required. Keep organized and work somewhere you won't mind making a little bit of a mess—not the good dining table!
STEP ONE - ASSESSMENT & DISASSEMBLY :
When you have an old, worn-out engine, or one with crash damage - it is necessary to identify what needs replacing. Generally, if the engine was running fine before a crash, you won't have to worry about things like the piston or ring, valve leakages, etc. Identifying a bent crankshaft or cracked case might be more important! If you are trying to resurrect a completely unknown engine it is important to check every aspect of the engine.
I purchased the subject engine on eBay, in a box lot of engines and parts. I didn't expect too much of the poor old Saito due to the photo, and when it arrived it looked to be in very poor condition. The front of the crankshaft was completely broken off in a crash. After I disassembled the engine and inspected the interior it looked very good, so I decided to rebuild it.