Mikuni Large Round Main Jets #137.5 4-Pack - Harley & Indian V-Twin
About Mikuni
Mikuni has supplied carburetors and fuel-system components to the motorcycle industry for decades, and its HSR series remains a common choice for carbureted Evolution and Twin Cam V-twins where a clean, tunable fuel curve matters more than electronics.
Precision fuel metering is critical for any V-twin, and these Mikuni large round main jets in size #137.5 deliver exactly that. Sold as a convenient 4-pack, they are essential for dialing in your carburetor's performance. Riders use these genuine Mikuni jets to match fuel delivery to engine modifications and changing riding conditions.
Why riders pick this
- Genuine Mikuni components for trusted reliability
- Exact #137.5 size for precise fuel metering
- Large round design fits compatible Mikuni carburetors
- Includes four jets for tuning versatility and spares
When you're chasing peak performance from your Harley-Davidson or Indian Motorcycle, proper carburetor jetting is non-negotiable. These Mikuni large round main jets provide the precise fuel flow needed for optimal combustion. Whether you've upgraded your exhaust, air cleaner, or are simply compensating for altitude changes, having the right jet size like the #137.5 is crucial for a crisp throttle response and strong power delivery.
Consistent Fuel Metering
- Genuine Mikuni components ensure reliable performance
- Large round design for broad compatibility with Mikuni carbs
- Precisely machined orifice for consistent fuel flow
- Convenient 4-pack for tuning and spares on the road
Tuning for Your Ride
Achieving the perfect air/fuel ratio requires careful tuning, and these main jets are a key part of that process. They control fuel delivery during mid-range and full-throttle operation, making them vital for street performance and long-distance cruising. Pair these with other Mikuni tuning components for a complete carburetor overhaul.
Specifications
- Brand: Mikuni
- Manufacturer Part #: FN100604-137.5
- Quantity: 4 per pack
- Length: 4.4 in
- Width: 2.2 in
- Height: 0.6 in
- Weight: 0.05 lbs
- Country of Origin: Japan
Common questions
What is the primary function of a main jet?
The main jet in your carburetor is responsible for metering fuel flow during mid-range and wide-open throttle operation, ensuring proper air-fuel mixture at higher RPMs and loads.
How do I determine if this #137.5 jet is the correct size for my V-twin?
Jet sizing depends on your engine's displacement, specific carburetor model, altitude, and any performance modifications. Always consult your Mikuni carburetor manual or a trusted tuning guide to confirm the appropriate jet size before ordering.
Will these jets fit my stock Harley-Davidson or Indian Motorcycle carburetor?
These Mikuni large round main jets are designed specifically for V-twin motorcycles equipped with Mikuni carburetors. Stock Harley and Indian models often use different carburetor brands and jet styles, so verify your carburetor brand and jet type before purchase.
Ordering from Vtwinbikers
- Brand new, sourced through authorized US distribution — never used, never grey-market.
- Not sure it fits? Use Shop by Bike to filter by your year and model, or email us and we will confirm before you order.
- Harley-Davidson and Indian Motorcycle is all we do, so you are talking to people who ride what you ride.
| BRAND | Mikuni |
| TYPE | Jets |
| SKU | 134-71375 |
| WEIGHT | 0.05 lb |
