This bike was 78.5, but was slapping the piston and had hairline cracks in skirt, I happened to have a 81.50 jug laying around that needed boring, so I took my dremel and cleaned up the ports and sent her out to be bored to 82mm, first let me complain that the guy was told to bore it to .004 clearance so I could do a long easy break-in, this guy gives it back to me and I can slide a .005 feeler guage along with the piston down the bore, a .006 will go also but it was real tight. The ring gap is at .025 well I went ahead and put her together, start it for about 60 seconds and listened for any problems. Then I checked the compression, it was at 140, I used only a single layer of the head gasket, trying to get the squishband reduced, I want to get it at .045. will need to do some milling and shaping to get it. Anyway, after a few heat cycles on this thing, I go ride her, after she is warmed up good, she will spark knock some at low to mid throttle. I am worried about it detonating and puff kaboom! Should I just go ahead and put race gas in her?