This is the cylinder contained in the 77cc pack but sold separately from its crankshaft. The 50mm diameter cylinder has 6 transfers as well as a wide bar exhaust outlet. The 39.2mm stroke crankshaft has an 85mm connecting rod which accommodates a 12x15x15mm needle cage. You simply can't go wrong buying this kit. Several people can testify to its solidity and its incredible quality/price/performance ratio.
Attention: Like the other kits in this category, you must mill the lower engine to be able to install the crankshaft and the cylinder.