and as said above the 54 outlines the bore size, but there is also a series of china engines with crazy numbers. like 53, lol there's no 53mm engine that i know of..
So theres no way to determine the manufacturer? Does manufacturer matter when purchasing internal engine parts? Google got me to this forum but still searching, thanks
99% internal parts are same or similar... of course with the exception of piston and crank sizes..
some engines have different primary gear rations too. then theres gearbox differences.
but in general all the minor parts are same...
shoot us a list of what ya want or are looking for and we'll go from there..
and also when googling your engine number, zongshen came up more than a few times... zonga and yx are pretty much the same... you could class the zonga engines as a glorified yx
edit..
can you show us some pics of the engine (both sides)
i have same problem i have a pitbike i got of my mate he said he brought a lifan 125 but when i checked the engine number was 154fmi, my mate said he defo brought a lifan 125 engine