Hey sajhw17, just rebuilding the top end and boring it out shouldnt change the jettting any. Unless it wasnt jetted right before you started. Its hard to guess on jetting cause it can change with elevation. You could have it dialed in perfect and change sea level and it would be way off. Something I used to do before I got a dyno was put in a new spark plug and then run it for about an 20 mins and pull it to see if the ceramic is a light tan which is good or if it is very dark to black would be too rich. Too light of a tan would be too lean. This may take several new plugs is the only down fall but you will have extra plugs that way LOL .