ORIGINAL: Tired Old Man
No worries. If the timing is off, it's prolly not enough to be a big deal and would not cause the sputtering anyway. Later in the troubleshooting process you can pull the carb and check that the reeds are seating correctly. There have been a few reeds from every reed maker that of late have not been seating on one side or the other.
Pat, I have to disagree with you here. More than one DL50 was having sputtering problems at our field and after finding the timing advanced 11 degs too far on one we set it back to 28, retuned, and it's ran great since. We later found a couple of others off by roughly the same amount and they were running quite bad as well. Setting the ignition timing and then retuning them fixed the problem with them as well.
In each case with the DL's they sounded horrible in the low and mid range and ran pretty good at WOT. With you having so much dyno time running these engines maybe you can help explain why the 11 degs of extra advance would cause them to run sooooo rough in the low and mid range and then they clear right up after setting the timing and retuning the mixture.
P.S. Pat, I am also curious as to whom might you might be refering to as "That experienced giant scale guy". Could you enlighten us? I've read and reread the posts and I can't find any mention of "experience" other than your post #12. It appears, IMHO, that everyone was trying to offer suggestions as to how the OP might be able to solve his problem and trying to do so without "degrading, insulting or embarrassing someone".