Has anyone drilled out the primary jet on KZ440?

From what I have found out there are two main jets on the keihin, a primary and a secondary. The secondary is under the needle and the primary is right next to it on the engine side. Under that primary jet is an emulsion tube that can get plugged up and will cause gas starvation. Is that starvation at lower rpms?. Once I am sure that emulsion tube is clear, I want to drill out the primary jet a bit. Has anyone done this to fix low rpm hesitation?

WAYYYY back when I was young, I drilled some jets to experiment and it's more trouble than it's worth IMHO.

Has anyone done this to fix low rpm hesitation?

On my bike, low RPM hesitation (stumble as throttle is opened) is most affected by needle position. The pilot jets also affect low RPM performance.


I have never worked on yours but that's how mine works.

The reason I am thinking about drilling it out is because I bought a jet kit and it includes small drills to drill it out if needed to dial the carb in. the kit directions say to raise the needle with 2 washers to start out with, and install a 102 secondary main jet, no change to the primary at this time. Then a fuel air screw adjustment and a test run. If problems persist in the low rpm range, its time to drill out the primary main jet, a larger one is not provided. From what they are called, I am assuming that the primary main jet is the first jet to have an affect on the response, then the secondary kicks in? At what rpm do they both operate in? I think I am having a problem with the emulsion tube underneath the primary jet. I think it is plugged and I can't get it out right now. I'll soak the carb completely again and see if it will break loose. Has anyone taken it out somehow? Does it just drop out after you unscrew the primary jet or do you have to unscrew it also?