Ok, so I bought this engine for my OCC bike from a guy on E-Bay (new, hadn't been run) and it says TIGER on the sprocket cover plate. I have no idea what exact size the engine is. Initially I thought is was 50cc. It does pull harder than the 47cc pocket bikes we've had, so I'm guessing now around 70cc? The cylinder head is more square shaped, not rounded like the 50cc engines I've seen. If anyone knows what size the TIGER engines came in, I'd appreciate some info. I could probably pull the head and measure the bore and stroke, but it's running really good, so don't want to mess with it. thanks.