why kickback afflicts cold engines?

"soft start cdi same 4° btdc"

The regular modules were 4 BTDC, but the soft start modules are 3 ATDC with the newer fly wheel. Kick back is usually easy to fix. It is usually only the few things I mentioned in the other post. Like I said don't keep starting and getting kick back or it WILL ruin the sprag clutch. Depending on what your idle rpm is set at when warm it may just be your starting technique or even a slightly weak battery or the carbs need some attenttion. It could be one thing or a couple of small things causing the issue. Things like plug gaps way too wide and needing a carb sync or idle set really low and then it would be better to crack the throttle during start.