Mikuni Large Round Main Jets - 4/PK #125

Genuine Mikuni large round main jets #125, sold in a 4-pack for carburetor tuning on V-twin motorcycles. These jets meter fuel flow at cruise and steady-state throttle positions, allowing riders to dial in the correct air-fuel ratio for their engine and elevation.

Features

• 4-pack quantity
• Genuine Mikuni OEM jets
• Large round body style
• #125 main jet size

Specifications

• Brand: Mikuni
• Manufacturer Part #: FN100604-125
• Jet Size: #125
• Quantity: 4 per pack
• Length: 4.4 in
• Width: 2.2 in
• Height: 0.6 in
• Weight: 0.05 lbs
• Country of Origin: Japan

Fitment

Fits V-twin motorcycles with Mikuni carburetors using large round main jet bodies.

Frequently Asked Questions

What does a main jet do?

The main jet meters fuel at cruise and steady throttle. Correct sizing ensures proper air-fuel ratio across the midrange and top-end RPM band.

How do I know if I need a #125?

Jet sizing depends on engine displacement, altitude, temperature, and carburetor model. Consult your carb tuning guide or Mikuni's recommendations for your specific bike.

Are these genuine Mikuni parts?

Yes — these are genuine Mikuni OEM jets manufactured in Japan, not aftermarket clones.

Why buy a 4-pack?

Having a range of jet sizes on hand lets you dial in the perfect air-fuel ratio without waiting for a single jet to ship. Common for riders who tune across seasons or elevations.