We have made a number of improvements to our long term Z400 test machine but have not done anything on the performance side. With sand dune season on the west coast now upon us, we decided we needed to give our Suzuki Z400 a little additional boost. We picked up a Team Suzuki Yoshimura slipon pipe and a Dynojet Stage 2 kit, and headed to the Dynojet Research and Development facility to see how they work.

There are a number of different configurations that you can go with, and a big difference in the power curve depending on which you choose. Before making any changes we did a base run on our stock Z400. The Z was peaking at around 30 HP. Next we tried the Z400 with the slip-on exhaust with the spark arrestor/quiet core installed and no jetting changes. The curve was very close to the all stock curve.

Of all the configurations we found the best power curve with the race core, the stage 2 Dynojet and the 146 main with snorkle endcap off. This gave big HP gains across the midrange - as much as 5 HP - and around a 2 HP gain on the top end. The gains were okay with the snorkel endcap on and a smaller jet, but not nearly as impressive as with the larger jet and snorkle endcap off.

Of all configurations with the Quiet Core/ Spark Arrestor installed, the best midrange was achieved with the Stage 2 Dynojet kit, snorkle endcap off, and the 146 main jet. This configuration gave some impressive midrange gains but fell off on the very top end (See the dyno jet Graph below.) and at peak gave around 31 HP. The Dynojet stage 1.5 kit with 136 jet lasted a little longer on the top end and gave as much peak power but did not look nearly as good in the midrange.

Summary - With the quick addition of a Team Suzuki / Yoshimura slipon and a Dynojet Stage 2 kit we were able to get some nice power gains across the midrange. Especially without the Quiet Core / spark arrestor installed. Many riding areas are starting to enforce sound limits and/or spark arrestors so you may be limited to the lesser gains with the quiet core until you head to the race track. The other benifet is some weight savings and a much nicer looking silencer than the OEM unit.