Jetting for Keihin CV

Pull the carb, change a jet, put it back, go and ride. Then do it again. Sorting out a Keihin constant-velocity carburettor by trial and error costs whole afternoons, and a box of jets you are never going to use. This app takes that road out of the way. Before you pick up a spanner, see what every change you are considering does to the mixture, and only fit the one that convinces you. WHAT YOU WILL USE IT FOR • You fitted a pipe, a filter or open intakes and the bike runs oddly. Try the change in the app and find out how far up you need to go before you buy the jets. • You are riding into the mountains this weekend. See how much richer it goes at 1,500 m and take the right jet with you. • You bought a used bike and have no idea what is inside it. Look up its factory jetting and compare it with whatever turns up when you open the float bowl. • You are torn between two needles. Compare both profiles on the same chart and see where each taper starts to work. START FROM YOUR BIKE, NOT FROM A GENERIC TABLE Pick make, model, year and market, and the app starts from the jetting THAT bike actually left the factory with, corrected for today's weather. The market matters: the same bike and the same year shipped with different jetting in Europe, in the United States and in California. Trust a table that does not tell them apart and you will fit somebody else's jet. 493 factory setups, 107 models: • Harley-Davidson (1980-2006): Sportster XL 883 and 1200, Dyna Low Rider and Wide Glide, Super Glide, Softail, Fat Boy, Heritage, Road King, Electra Glide. • Honda (1982-2007): CBR 600F, 900RR and 1000F, CB 400 Super Four, 500, 600F Hornet and 750 Nighthawk, VT 600, 750 and 1100 Shadow, VF750C Magna, VFR750F, VTR1000F, ST1100 and GL1500 Gold Wing. • Kawasaki (1984-2009): ZX-6R, ZX-9R, ZZR600, ZRX1100 and 1200, GPZ900R, GPZ500S, EX500, Ninja 250R, Zephyr 750, Vulcan 750, 800 and 1500, Concours 1000, ER-5, ZR-7. • Triumph (1995-2008): Bonneville 790 and 865, T100, Thruxton, Scrambler, America, Speedmaster, Thunderbird, Trophy, Trident, Tiger, Sprint Sport. • Yamaha (1994-2007): FZR600R, YZF600R Thundercat, YZF-R6. • Suzuki (1994-2004): GSF600 and GSF600S Bandit, GSX-R750. YOU SEE WHAT HAPPENS, NOT ONE LOOSE NUMBER The chart draws the mixture across the whole throttle, from idle to wide open: lean at the top, rich at the bottom. Overlay as many setups as you like and see at a glance where they part company. Below it, the table gives the difference as a percentage over three ranges — low, mid and high — which is how this gets talked about in the workshop: "it runs lean at half throttle". THE NEEDLES, MEASURED ONE BY ONE Keihin never published needle dimensions for this family. Nobody has them. So they have been measured, point by point, and the app carries their real profile: where the straight section ends, how steeply each taper falls away and how far every shim lifts it. Search by code or by bike, compare two profiles on the same chart, and tick the needles and jets you actually have in the workshop so the lists only offer what you can fit today. A CV IS NOT A SLIDE CARB And the app is built knowing it. Here the grip moves a butterfly and it is venturi vacuum that lifts the piston. The mixture screw is a FUEL screw: opening it enrichens, the opposite of a racing carb, and that single mix-up has ruined plenty of idles. The needle has no clip: it sits on its seat and only rises on shims. ALSO • Weather by hand or from the nearest station, with air density and density altitude. • Metric or imperial units. • Help on every screen, explaining which way each part moves the mixture. • Six languages. iPhone and iPad. Works offline except for the weather lookup. The model is comparative: it measures one setup against another, which is exactly what you need to decide on a change. It does not replace a road test or reading the plug. An independent app, not affiliated with Keihin or Hitachi Astemo.