Originally, it ran okay when I had it with the kit "X" & "Y" pieces used with the airbox in place & standard plumbing. I`d drilled loads of holes in the airbox lid and the centre dividing section inside the clean bit.
I only ever ran with it jetted very rich. So it would hit a flat spot in the mid range. Revved out okay though.
I thought it would have just needed tweaking a bit on the needles & dropping the mains slightly then.
When it seized when you were playing with the jetting, which cylinder went Mark?