If you plan to work on your chinese bicycle engine, you need Super Magic Tool. Technicians call this a Specialized Service Tool, or SST; but I like SMT better. If you bought the engine as a kit, it probably came with SMT. If not, do not attempt disassembly/assembly without it. Pick one up for three bucks.
It is the fucking bees' knees.
The engineers that designed this engine cleverly threaded just about every shaft, passage, hole with one of three sizes of fine threads. SMT can be installed into or over any of these. It is a press, a puller, and an alignment tool, all in one.