Jetting for Honda CRF 4T Moto app for iPhone and iPad

2002-2021 models
This app provides, using temperature, altitude, humidity, atmospheric pressure and your engine configuration and fuel type, a recommendation about best jetting (carburetor configuration) and spark plug to use for Honda 4-strokes MX bikes (CRF-R and CRF-X models) with Keihin FCR carburetors.

This app can obtain automatically the position and altitude to get the temperature, pressure and humidity from the nearest weather station thought internet. Internal barometer is used on supported devices for better precision. If more accuracy is needed, a portable weather station can also be used. Application can run without GPS, WiFi and internet, in this case user has to give the weather data manually.

• For each carburetor configuration, the following values are given: main jet, needle type, needle position, pilot jet, air screw position, spark plug
• Fine tuning for all these values
• History of all your jetting setups
• Graphic display of fuel mix quality (Air/Flow Ratio or Lambda)
• Selectable fuel type (gasoline with or without ethanol, Racing fuels available, for example: VP Racing T4, U4.4, MR12, Sunoco 260 GT Plus, EX02)
• Adjustable fuel/oil ratio
• Mix wizard to get the perfect mix ratio (fuel calculator)
• Carburetor ice warning
• Possibility of use automatic weather data or a portable weather station
• If you dont want to share your location, you can manually select any place in the world, the carburetor setups will be adapted for this place
• let you use different measure units: ºC y ºF for temperatures, meter and feet for altitude, liters, ml, gallons, oz for fuel, and mb, hPa, mmHg, inHg atm for pressures

Valid for the following models from 2002 to 2021:
• CRF150R
• CRF250R
• CRF250X
• CRF450R
• CRF450X

The application contains four tabs, which are described next:

• Results: In this tab main jet, needle type, needle position, pilot jet, air screw position, spark plug are shown. These data are calculated depending on the weather conditions and the engine configuration given in the next tabs.
This tab lets do a fine tuning adjustment for all this values to adapt to the concrete engine.
Besides this jetting information, the air density, density altitude, relative air density, SAE - dyno correction factor, station pressure, SAE- relative horsepower, volumetric content of oxygen, oxygen pressure are shown too.
On this tab, you can also share your settings with your colleagues, or add settings to your favorites.
You can also see in a graphic form the calculated ratio of air and fuel (lambda).

• History: This tab contains the history of all carburetor setups. If you change the weather, or engine setup, or fine tuning, the new setup will be saved in history.
This tab also contains your favorite settings.

• Engine: You can configure in this screen the information about the engine, that is, engine model, year, spark manufacturer, fuel type, oil mix ratio.

• Weather: In this tab, you can set the values for current temperature, pressure, altitude and humidity.
Also this tab allows to use the GPS to get the current position and altitude, and connect to an external service (you can choose one weather data source from several possible) to get the weather conditions of the nearest weather station (temperature, pressure and humidity).
In addition, this application can work with a pressure sensor built into the iPhone. You can see if it is available on your device and turn it on or off.
Also, on this tab, you can manually select any place in the world, the carburetor setups will be adapted for this place.
Moreover, on this tab, you can enable alerts about possible carburetor icing.


If you have any doubt about using this App, please, contact us. We answer every question, and we take care of all comments from our users to try to improve our software. We are also users of this application.