what is the difference between attempting to bore a stock cylinder to 72mm and a factory made 240 BBK? why is it that you can not bore a stock cylinder over say roughly 68mm? a 240 kit has a very thin cylinder wall after all.
There actually is not enough material inside of a stock sleeve to go to 72mm piston bore size. A stock cylinder can have another sleeve installed that CAN be "bored" to 72mm but it basically involves completely cutting out the old sleeve and installing a new one into just the aluminum left after the iron sleeve is gone.
Interesting information there, Civic. I didn't know that about the big bore sleeves. I just never really thought about it but if the sleeve was bigger all the way down, the cases would have to be bored too. I know some of the Honda 250 BBK require the cases to be "opened up", I guess that's why. On the Blaster engines that are 265cc, are the cases bored to accept a sleeve that has a larger OD sleeve down into the cases?
to the OP:
If ya haven't check out this post!
http://www.blasterforum.com/engine-13/yamaha-blaster-cylinder-cut-away-learning-tool-50894/