I have finally opened my Global Engine to check the size : the heads seem fine, the valves and rockers are good. The cylinders show a few scratching marks, but should be ok. I have more concerns for the pistons that have thick black deposit and rust. I should clean up the rust... and the piston arrow is towards the rear (pointing the pilot seat).
The size? 78mm by 92mm, so 1034 cc and should deliver about 37hp.
Engine number is 0884 A022 78.