from what ive heard, it is legal now to increase the bore size, but not the stroke....and ive also read that without stroking, a 139cc motor runs better than a 144 because the piston is lighter, allowing it to rev a lot faster....so if you're going to bore out your 125, i suggest you bore it to 139 rather than 144, not that its going to help much against the 250f's anyway
