Because the cubs are nickel plated there isnt as much need to warm up the cylinder as the steel the cubs are plated but still aluminum just like the pistons therefore they expand at the same rate, the steel liner expands at a slower rate than the aluminum piston, thats why you hear of guys cold seizing motors because the piston expanded faster than the cylinder. Ive been to alot of drags with Calvin and I gaurantee you he never breaks in anything or warms anything up, on his nickel cylinders of course. He just dont believe in it. Not by any means saying not to warm up a bike I do it everytime but thats what the man that built the cylinders do??