Yes stroking the crank it is...

You relocate the pin holding the rod away from the crank, so you increase the stroke to get more cc's.

The problem is that crank on NSR seems a little snug fit in the cases and the

pin also seems it cant be relocated much out... thats why i ask maybe someone has tryed or something, so as to find out what is waiting me...

I am not afraid about rods you can find lots of them and exactly as you want them.