86 xt600 stumbles off idle

[Live42day]

I've got an 86 xt600 I bought non running. The po said it ran great but studdered on acceleration. I cleaned carb full of powder including float valve filter replaced float valve seat and valve, replaced diaphragm thoughrly cleaned carb 3 times through the process of trying to sort this. Adjusted secondary so butterfly is horizontal at wot because 5-7mm was way past horizontal. The bike starts 2nd kick every time idles great revs great but when ridding it Boggs just off idle and eventually clears up. It's a great 2nd gear trail bike at the moment because it'll lug along great and accelerate well but on the road it's sketchey due to the hesitation. I checked for air leaks and found none, new air filter and plug. Tested everything electrical I could with multimeter and everything was within spec. I have a parts bike I swapped cdis with and got the same results. What am I missing?
Also plastic Clarke tank and new petcock
After a little more digging I'm seeing the ignition is supposed to fire at 2 different places. Does anyone know what controls this? I've seen it mentioned in a couple places but no one has explained how this works and I'm not seeing it in my manuals.