Carb adjuster problem

[Ignis]

I installed a 38mm carb on my 1986 X2 to replace the original 28mm one that was on there. Question, the high speed adjuster does not seat! Instead it just turns & turns and never tightens! Does this mean the threads are stripped in the carb? If so, is the carb trash?

Also, with just bolting this onto the ski, I havn't really noticed any improvment. Do I also need an aftermarket pipe before I see improvements? Are some pipes better than others?