The ZX9R like many bikes are toned down to pass EPA requirements here in the states. The need to let the bike breath a bit necessitates a jet kit and although Factory jet kits have been my choice in the past, many ZX9 owners have used Ivan's kit with much success. Ivan's site has all the info on his jet kits and additional accessories. The kits are not your normal drop in kit BUT you won't have to tinker with it once installed so pick your poison. Ivan's philosophy is based on streetability and he put 8 months of Dyno and street time into the kit for the '98-'99 ZX9R. The kit includes everything...minus tools needed to get the carbs off. Preferably with the service manual remove the tank and carbs...so they can be gutted ;) The Ivan's kit also recommends a +4 ignition advancer, stock air filter, and if a full pipe is used....a 4->1 full header or stock header w/stock pipe or slip-on.

PARTS NEEDED: +4 ignition advancer recommended, service manual recommended for backup informational purposes.

1) With the carbs off the fun begins. Follow the instructions EXACTLY...otherwise bad things will happen to parts of your carbs that are not supposed to be touched. First thing is removal of the pilot air jet...which as described in the instructions (the pressed in orifice to the left of the needle under the velocity stack). There is a tap included in the kit that will remove the air jet and it only fits the correct one..so that might steer you in the right direction if there's any doubt. I used a pair of pliers against the body of the carbs to get the proper leverage to pull out the air jet. Do whatever works for you...just be careful !!!

2) Float level adjustment, main jet change,and set the mixture screws. You have to change the float level to 14mm, a very slight bend of the tab will do the job...try not to over do it. I ran a full Ti Muzzy's exhaust system ( later changed it to an Akrapovic system ) so a 160 main was in order. It's a very easy change..just don't tighten it too much. The instructions explain how to remove the plugs if they exist...otherwise I set my screws to 4 turns out as per the instructions.

3) New needles, drill the slides, and clip the springs. I put the needles in at the third position from the top as in the instructions, used 3 washers per needle, and put them back in with the stock holder. There is a drill bit included in the kit to drill out the air diffusion hole on the bottom of the slides. The bit will very slightly drill it out...and just a few turns by hand will do the job. I didn't clip the springs...but that's because the springs I had were not stock. If your springs are stock go ahead and clip off 1/4 in and bend the top coil downward slightly as in the instructions.

4) Last but not least...remove the intake and exhaust air circulation. The instructions detail how to disable the systems...I'd rather just remove them completely. Remove the vacuum valve and the valve below it that connects to the valve cover. The upper vacuum valve connects to a few different places ...just plug the holes with vacuum plugs.

The hose that I'm holding below can be recycled to plug the KLEEN exhaust air recirculation system.

Remove the hose from the vacuum valve and place it between the rubber hoses as shown on the next page. I used some silicon sealant where the rubber hose meets the attachment to the valve cover.

Buy a piece of 3/8in fuel line to connect the hose from your carb breather tube to the hose that previously connected to the vacuum valve(will need a male to male vacuum hose at an auto parts store). If you trace the hose forward it connects to the small scoops inside the RAM air scoops. They're primarily used for carb breathing but have been also used to bring fresh air into the smog equipment on US models. Synch the carbs and you're done !!! Put your bike back together and go ride your new bike ;) It'll feel like a new bike....

UPDATE as of 10/7/2004: My setup has changed to 3.5 turns out on the pilot screws. Cold startup in warmer weather was too rich using the choke yet not quite enough to start with no choke. The main stands @ a 160, needle is @ 3 slots from the top, and pilot jet is the stock 38.

Addendum for the '00 ZX9R

I totaled the '98 ;) and acquired a '00 ZX9R......mmmmm more compression and horsepower. An Ivan's kit was in order because it buzzed like a bee and was running WAY too rich. Finally I got it and found some pros and cons to the '98 kit. First I noticed that the float height remains stock, no spring clipping, and no slide drilling....cool. It went downhill from there...ie. not only do I have to pull the pilot air jets but I have to thread the remaining caverns to take a 110 jet. ICK...that doesn't sound fun at all. The remainder of the kit is exactly like the '98 in that the needles get replaced, only the inner 2 mains go down to a 160 from a 165, and the pilot screws get set to 2.5 turns out. Since all that is a repeat I'm not going through it...here's the nitty gritty on the pilot air jets though.