Clapped out SV650, previous owner said it was a stock motor: I CC'd the heads, and got 18.9 and 18.6 CC's, so that seems to check. I'm planning to mill the heads, rough estimate of .015/.012 to get into the 17.7CC range (looking to use pump gas, 12:1 CR). Eye balling that distance with the end of a caliper, it looks like it would just barely cut into the intake valve seat insert. Is that normal? Or are my eyes playing tricks on me?
I've seen SV heads come into my shop milled 0.040", running fine. It's not the way I would do it, but it does work. 0.015" is conservative, don't be concerned.
Thanks for the help. Since you're awake, I'm tentatively planning to just set squish at .040 and call it a day. But I did throw some Carillo A beams at it while the cases were split, how far can I actually push squish before I'm just being greedy/stupid? Since I estimated the required head cuts based on a complete cylinder, the .015 will fall short of an actual 17.7CC. Just wondering if it's even worth screwing with, or just stick to the .040 gameplan.
You can reduce the squish slightly further safely, but as you keep going, you get less gain and more broken cranks.
Thanks for the advice .015 off the heads and middle layer out of the head gasket worked well, bike is back on track and ran well today.
