Miss matched set up/pipe
You went from a low end pipe to a hi rpm pipe, you need to tune clutch to get into the power band.
On a simple one speed engine with your set up (?) you should’ve stuck with the low-end pipe, maybe upgrade to a estoril or techo circuit for that treats pipe is best for big kit, big carb super tuned clutch etc.
Your jetting should be close to the same (82 seems too big to begin with) size, maybe a size or two bigger, you may have to mess with the needle and slide but without knowing what your set up is, what your clutch is, or what you’re timing is who knows