...Followed the ProCycle instructions to the letter....
Including the last part? Where it talks about testing and tuning the setup for your particular bike?
The setup you have will work great once it's tuned.
When you twist it rapidly, vs very slowly, does it behave the same? What clip position, main jet, fuel screw turns out are you using? Is your airbox stock? Is the exhaust stock? What air temperature and altitude? Did you check/set the float level?
There are a lot of things that impact jetting. The more details you can share, the faster folks can help you. No worries what you have done or not done. No worries what you know or are confused about. I'm happy to help!
Not enough information yet to give a specific response.
OK, thanks for the feedback, here goes ... it only stumbles when twisted rapidly.
Stock exhaust, airbox and filter. Filter is clean, almost new.
Air temp is about 65, altitude about 445'
Here's what was done to the carby:
Dipped and sprayed all channels over 3 days
Removed 140 main, replaced with 150
Remove, clean reinstall 42.5 pilot jet
Remove, clean and reinstall main air jet
Pilot screw 1 ½ turns out
Reset front float height to 15mm (versus stock 14.7mm)
Replace original jet needle w ProCycle kit, set clip on groove #4 from tip of needle.
New o-ring & washer
Drilled 2nd hole in slide
New hex bolts on carb cap & float bowl
New gasket on float bowl, new o-rings on float