the weather looks great that time of year actually. for some reason I cant post a link but I googled it
75* high and 53* low
14% chance of light rain in early october
Switch plug wires and see if it switches. Done a compression test?
Reeds could be wore out.. sometimes even look ok. Swap them and see if it follows. Jet could have got clogged from something in fuel line.
Might I add that you should have your cyls measured to see if you need to bore them. Just honing and new pistons could cause a loose fitment and problems down the road..
I would do the 4mm keeping the stock carbs but get the vf reeds and the timing plate now. You will enjoy it.. then later if you want a little more get the bigger carbs.