I know very little about this, but I will offer advice where I can...
Oil the filters. What I did was over-oil the filters, and (with the pk-92) I put the filter boot on a table, compressed the whole filter down, grabbed a rag, and gripped/squeezed the foam.
I can't wait to figure out what the problem is, but I'm going to put my bet on too much air flow.
These bikes need air restriction to operate properly. With no air restriction, the vacuum assembly doesn't work right.
Probably not your issue, just my guess
Also double check vacuum caps. Is your left vacuum in stock position (petcock to carb)?
Check your plugs, they might give you an indication, but I don't know.
I'm just a troll 'round these parts