hey i found this and i thought it may help a few cag owners
The first way to tell is to look at the 4 fins on the bottom of the cylinder
head. The bottom 4 cooling fins on the 40cc engine join right the way
around the cylinder head, with no break in between them. Whereas the
bottom 4 cooling fins on the 49cc engine stop at the corners and don’t go
all the way round.
Take a look at the picture of both the Cylinder heads below:
The cylinder head on the left is a 40cc engine - look at the circled bit at the bottom 4 fins, you can see they are joined all the way round the
cylinder. The cylinder head on the right is a 49cc engine - look at circled the bottom 4 fins, you can see that there is a break in the
fins.
hope this helps
cheers nick
How to check if your motor is a 49cc 
Linear Mode
