Only pull the spark plugs if you know that the magneto safety gaps are set properly. The gaps are there to allow the spark energy to find ground if something happens to the spark plugs or wiring. If the energy can't get to ground, damage to the coil can happen.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
You don't have to guess whether you have too much differential timing. Use an Ohm meter to determine exactly when the points open each time relative to the S mark on the flywheel. More than a couple of mm difference between each cylinder is too much and can be corrected as described previously.
Hmm, I don't think so, this came after adjusting points and carburetors. Now, how to fix it is what I don't know.
When an issue appears after any recent maintenance work, before you go hunting for a mysterious cause, take a look at the work last completed. You said it appeared after adjusting points and carbs, therefore differential timing makes no sense as a possible explanation. Often the simplest explanation is correct.