The engine in the 140SR is the 55. We tested both but preferred the Lifan (55) over the YX (56) engine. Not sure if I'm allowed to use this pic or not (mods pls delete if I'm breaching copyright) but here is our SR out front at the Mini SX with the only mod being an engine kit!! behind are some worked verts plus a few other hot rods.
If you ever have questions about our bike feel free to email us and we'll do our best to answer them.