Is this a final jet size?
No. It is a starting point. Confirm by throttle response and plug color, especially on a modified engine.
ATV Calculator
ATV Carburetor Jet Size Calculator
Get a starting main-jet number when you ride at a different altitude or temperature than the baseline jetting.
Results
Values update after you calculate. Empty or invalid inputs will not invent a number.
Enter the values and choose Calculate to see estimates.
How it works
Air density falls as altitude rises and as temperature rises. The calculator scales the stock jet by the square root of that density change.
Estimated jet = stock jet × √(relative air density), using about 3% density change per 1,000 ft and absolute temperature.
These results are estimates for planning only. They are not OEM specifications, safety certifications, or professional mechanical, legal, or financial advice.
Carburetor Jet Size Calculator FAQs
Do I go down a jet at altitude?
Usually yes, because thinner air needs less fuel. This page estimates how far to move from the stock number.
What about needle and pilot jets?
This calculator only scales the main jet. Pilot, needle, and air-screw still need separate tuning.
Related ATV calculators
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Calculate ATV air-fuel ratio and lambda from air mass, fuel mass, and fuel type.
Engine Displacement Calculator
Calculate ATV engine displacement in cc, cubic inches, and litres from bore, stroke, and cylinder count.
Fuel Injector Size Calculator
Estimate ATV injector flow in lb/hr and cc/min from horsepower, cylinder count, duty cycle, and fuel type.
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