He kicked again.
Since the 253FMM is a "clone" engine, the specifications in most manuals are highly accurate for major mechanical tasks. Engine Architecture 253fmm service manual
Widely available for free or purchase on sites like ManualsLib or iFixit. He kicked again
The 253FMM is typically a 233cc or 249cc air-cooled, 4-stroke, 8-valve (or sometimes 4-valve) SOHC parallel-twin engine. 253fmm service manual
A detailed ML250-4 Engine Parts Catalogue provides exploded diagrams of the 253FMM cylinder head, crankcase, and transmission.