[Sparko]

if you're trying to keep cost down by not having a shop diagnose this, I'm not sure why you gave up at checking rockers. Compression, timing, and spark are simple low cost checks that don't take much time. Have you drained any of the oil out since this problem surfaced, is there any metal in the oil? A recording of the noise would also be of help, engines can make a lot of different noises.