CG125 engine swap - to mbx125

I have the chance to buy a running mbx 125 engine (basically an mtx 125 engine with longer gears) for £50 with the carb which is a real bargain. Anyone ever done this swap before? I love my CG but the 10bhp it make is very limiting and the MBX makes 20bhp. I understand an engine swap is not just take one out put the other in, but there from a similar time and the same engine size. Sadly I cannot measure it up as it would have to be posted to me...

i put a xr125 engine in my cg 125 one thing to note is how old is your cg 125 ? some of the older ones used points and some were 6 volt the newer ones were cdi ignition which i would assume the mbx engine is too ? is the mbx one of the chinese engines based of the cg engine or is it the overhead cam type based of the cb 125 engine? or is it something totally different ?

Totally different engines if you are talking about the 80's 2T. It might be more hassle then it is worth to put that engine into a CG.
A better option might be to find a larger Chinese Honda knock off and put that in. I know Lifan make 250cc engines that look as if they may mount the same.