I was contacted by Mike's XS and offered a free set of "XS Performance" carbs in exchange for an honest assessment of them. They told me that there have been many satisfied customers but admit that they are of inconsistent quality. If you get stuck with a lemon, they will exchange it.
I was hopeful that the original set of "Keihin" carbs I got were just duds and the new "XS Performance" carbs would work well. Looking at them side-by-side, they appear to be identical carbs with just a name change.
In fact, Mike's confirmed that the "XS Performance" carbs come from the same factory [in Taiwan] as the "Keihins" that Mike L. was selling. The only change is the name on the side and the cable adjusters.
From the looks of it, they have been using the same tooling all these years without resharpening anything.
Those are pics of the slide bores of the "XS Performance" carbs right out of the box. The finish is atrocious! Worse yet, the slides rattled around inside. There was about 0.015" slop. Compared that to the slides in my "Keihins" which were about 0.005".
Another indication of the hit and miss quality is this accidental drill mark.
It doesn't look like that big of a deal except that that is where the o-ring for the jet block is supposed to seal.
Despite all that, would you believe me when I tell you that the carbs worked flawlessly? No really, the overly rich off-idle transition is gone [using the jets and needles from my other carbs] and the slides did not stick. Well, for the first ten minutes anyway. They were sticking before the end of the first test ride. I re-synced them and went for another ride. By the time I got home they would stick while parked [revving the engine in neutral]. However far I opened the throttle, that is where the slides stuck. I confirmed that it was in fact the slides sticking by reaching down and moving the cable housings up and down in the adjusters.
When I reported to Mike's XS that these carbs were also duds they offered to pay me for my time.
The new owners are trying. I'm told that the future kits will have a better quality cable and they have a guy in Taiwan now to try and get a handle on the inconsistent quality issues with the carbs.
I hope they can get these ironed out. When they work, they really work quite well. It is a nice design and very easy to tinker with. I am told that there are some decent ones out there but I have yet to personally see it.