Khun Akkarat, has just dragged his dad's old 125cc two-stroke motorcycle out into the daylight. It's been in hibernation since his dad had some eye problems, many years ago and he asked what's likely to need attention before getting it going.
A lot of good advice came back; spray light oil down the spark plug hole and turn the engine slowly on the kickstart to ensure it's free; drain the old engine oil and replace it with cheap stuff (and a new oil filter) to act as flushing oil; remove the old rusty drive chain and replace it with a shinny new one.
We suggested an alternative of turning the engine over on the kickstarter while in second gear and standing with the rear wheel off the floor, for a few seconds at a time to circulate oil around the engine. It's worth changing the oil and filter first because dirt will have settled to the bottom and shouldn't be stirred up. Also, old oil filters sometimes disintegrate, causing catastrophic oilway blockages. The Mikuni RM22 SC carburetor will probably need a strip and clean, but khun Akkarat should be careful not to break any gaskets or O-rings, which can be difficult to replace (not much parts suppliers stock two-stroke parts now-a-days). He might get away with filling the carburetor with fresh petrol, and using the drain screw to flush it out.
If the motorcycle has contact breaker ignition, the points will probably be furred up and will need polishing with wet-and-dry paper. It's best to take them off to do this, first noting where the various insulating washers fit on the wires. It's easy to misplace them and lose your spark.