Displacement discrepancy

Hey guys, new member again...as some of you may know, I am a new member tearing down my new pocketbike, mostly due to the fact that's its febuary in northern Alberta...It ain't being ridden any time soon!
So anyways, the owners manual that was given to me with my cag proclaims that it is a "Minibike-WQ-0 1"... It says in its basic technical data that it has:
A "working volume" of 49.9cc's...ok so I assume they mean displacement...
Power output of 2.5kw @ 8700rpm
11,000 max rpm
Dell Ortoro carb...

Now my problem is that with everything I have been reading, I have assumed that the 49cc cags have 44mm pistons... now I have ripped off the cylinder from the piston and measured accross...40mm!!!
What Gives?! Wrong generic manual or what? Are all the Cags stroke the same?! cause it doesn't say...
Now...how do you go about measuring your "wrist pin"... which as I understand, is a measurement you need for ordering a BB kit...cause now that I see that I have "only" a 40mm piston...I've been thinking...
Thanks guys...

dont believe the chinese manual.. thats like believing there is no cat in the all you can eat General Tzo buffet...

Oh yeah, by the way, thanks to the wisdom of the board, I have lightened and balanced my flywheel, balanced my clutch "arms," ported and polished my carb, modified my velocity stack, tapered my carb needle and learned about jetting...ALL FOR FREE!


HEY!!!! CAGARONI!!! Man, I have been doing some serious thread digging...you deserve some respect... I've learned a lot from you guys...

OK...I can't seem to edit my posts again but anyways...I have since learned that I have a 10mm piston pin...

FWIW, I would stick with the 40mm top end. They rev a lot higher than the 44mm top ends; if you want to do things right, DDM has a 40mm ADA headkit, which will give you the increase in torque from the better 2-piece head design, along with the top end of the small bore engines.

Too bad you are in Alberta. We've been racing regularly on an indoor kart track here in Winnipeg. Stay warm!

You know...I saw kit on Dave's...hmmm, something to think about for sure...thanks for the tip...
As for the indoor track...Now THAT would be the sweetest! Gear up, no fear!