As the SuperTrapp FAQ recommends, you should alter the number of exhaust diffusers, ride and determine if performance is more or less to your liking. Well, I now have a tool to take the guesswork out of the equation, confirm riding impressions, but arrive at the same desired result. This time, there's no arbitrary seat-of-the-pants impressions that could go either way. A wide-band Lambda sensor will give me 100% absolute real-time air to fuel ratio numbers to tell me how well I've tuned my Supertrapp and thus, my carburetors.

The AEM wide-band Lambda AFR digital readout and O2 sensor (30-4110*) was installed last year on my 900 Ninja (ZX-9R). I recorded many of the results over a variety of riding conditions. Last years readings however were on a different motor, running different engine coolant. Since it was cheaper to swap to a younger motor than to even replace the oil seals in my 128,000 mile motor, I now have a much lower mileage motor, but also running waterless engine coolant.

The combination of light oil leakage fouled my original AEM O2 sensor and eventually burned out the digital Lambda readout. One warranty replacement later, it's all working again and I have new numbers, different from before even though my carburetor jetting is mostly unchanged from before. I've confirmed my mid-range jetting is too lean, 15.2:1 lean at 55 MPH. Conventional SuperTrapp FAQ wisdom says to remove one or two diffuser plates to boost performance, get the AFR back below 14.7:1. Only this time, when I do, the AFR readout will tell me how much closer I am to ideal. My plan is to tune either only my SuperTrapp and/or my mid-range jet needle height to arrive at more ideal AFR numbers that I was seeing from the bike last year.

For those wondering or a bit puzzled about how an AFR readout got on a carburetted motorcycle, it's aftermarket.




* 30-4110 is the full kit. The cheaper 30-4110NS version stands for No Sensor, as in no O2 sensor.