Mikuni Jet Size Chart & Drill Size Guide
This guide provides a practical reference for Mikuni carburetor jet sizes and drill sizes commonly used for cleaning, checking, and careful tuning work. Mikuni jets may be identified differently depending on jet style and application, so this guide should be used as a practical drill-size reference rather than a guaranteed manufacturer specification.
About Mikuni Carburetors
Mikuni carburetors are widely used on motorcycles, ATVs, snowmobiles, personal watercraft, and many other powersports and small-engine applications. Depending on the carburetor series, they may use several different jet types, including main jets, pilot jets, slow jets, and other calibrated fuel metering components.
Mikuni jet sizes are commonly identified using metric-style numbering, but jet numbers are not always directly interchangeable between different Mikuni carburetor families or with other carburetor brands. Always verify the specific jet type and application before using a drill for cleaning, checking, or careful tuning.
Which Drill Set Is Right for Mikuni Jet Work?
For many Mikuni jet cleaning, checking, and careful sizing jobs, start with the smallest range that covers the jet sizes you need.
Best Starting Point: 20 Pc Selected Sizes Carburetor Jet Drill Set
Covers selected sizes from .0135" through .071", including many small metric and numbered drill sizes commonly used for carburetor jet cleaning, checking, and careful tuning.
Need More Continuous Size Coverage?
The 25 Pc #75–#51 Carburetor Jet Drill Set gives a broader numbered-drill range for general carburetor jet checking, cleaning, and careful tuning.
Want Backup Drills in Each Size?
The D7 50-piece #80–#56 set includes 25 sizes with two drills per size, which is useful when working with small, brittle carbide drills.
Working on Larger Jets or Multiple Carburetor Brands?
If you work on larger carburetor jets, Holley-style jet ranges, Ford Model A Zenith carburetors, or several different carburetor brands, compare the full collection before ordering.
Important: carbide drills are brittle precision tools. Use light pressure, keep the drill straight, and avoid enlarging jets unintentionally during cleaning.
Mikuni Jet Size Chart & Drill Size Reference
Many Mikuni jet references use metric-style sizing, where a size such as 100 is commonly treated as approximately 1.00 mm for practical drill-size comparison. However, Mikuni jet numbering and actual fuel flow can vary by jet type, carburetor model, and manufacturer reference, so always verify the jet and application before modifying anything.
| Jet Reference Size | Metric Reference | Approx. Inches | Nearest Common Drill Reference |
|---|---|---|---|
| 50 | 0.50 mm | 0.0197" | #76 |
| 55 | 0.55 mm | 0.0217" | #75 |
| 60 | 0.60 mm | 0.0236" | #73 |
| 65 | 0.65 mm | 0.0256" | #72 / #71 range |
| 70 | 0.70 mm | 0.0276" | #70 |
| 75 | 0.75 mm | 0.0295" | #69 |
| 80 | 0.80 mm | 0.0315" | 1/32" / #68 range |
| 85 | 0.85 mm | 0.0335" | #66 |
| 90 | 0.90 mm | 0.0354" | #65 |
| 95 | 0.95 mm | 0.0374" | #63 range |
| 100 | 1.00 mm | 0.0394" | #61 |
| 105 | 1.05 mm | 0.0413" | #59 |
| 110 | 1.10 mm | 0.0433" | #57 |
| 115 | 1.15 mm | 0.0453" | #56 range |
| 120 | 1.20 mm | 0.0472" | #56 / metric drill range |
| 125 | 1.25 mm | 0.0492" | metric drill range |
| 130 | 1.30 mm | 0.0512" | #55 range |
| 135 | 1.35 mm | 0.0531" | #55 / #54 range |
| 140 | 1.40 mm | 0.0551" | #54 |
| 145 | 1.45 mm | 0.0571" | #54 / #53 range |
| 150 | 1.50 mm | 0.0591" | #53 |
Note: This chart is an approximate drill-size reference. It should not be treated as an official Mikuni specification or a guaranteed fuel-flow conversion.
Using Drill Sizes for Mikuni Carburetor Jet Work
Precision drill bits are commonly used in carburetor work for cleaning clogged jets, checking approximate jet size, comparing jet openings to known drill diameters, and carefully modifying jet orifices when tuning requires it.
Because drills come in fine size increments, they provide a practical way to work within small carburetor jet size ranges. When modifying jets, make small changes and verify results carefully.
Practical Drill Size Range for Mikuni Jets
Many common Mikuni jet references fall within the small numbered-drill range used for carburetor tuning work. For this reason, a 20-piece, 25-piece, or D7 50-piece numbered drill set may be a better starting point than a larger Holley-focused range, depending on the sizes you need.
If you are unsure which set is best, compare the carburetor jet drill sets before ordering.
Choosing a Carburetor Jet Drill Set
Different carburetor jobs may require different drill ranges. A larger set gives you more coverage, while a smaller selected-size set may be enough for common cleaning, checking, or tuning work.
- 20-piece selected-size carburetor set: a practical starting point for many small carburetor jet jobs, especially where selected metric and numbered sizes are enough. View 20-piece set →
- 25-piece carburetor set: covers a broader numbered-drill range for general carburetor jet checking, cleaning, and careful tuning. View 25-piece set →
- D7 50-piece #80–#56 set: includes 25 drill sizes with two drills per size, useful when you want backup drills in each size. View D7 set →
- HS1 50-piece Holley-focused set: covers a larger .040"–.125" range and may be useful when larger jet reference sizes are needed. View HS1 set →
- Ford Model A Zenith set: selected for Ford Model A Zenith carburetor jet work. View Ford Model A Zenith set →
Compare Carburetor Jet Drill Sets
Tips for Jet Sizing and Modification
- Use light pressure when working with carbide drills
- Keep the drill straight to avoid making the jet opening oblong
- Always verify size before modifying a jet
- Make small, incremental changes when tuning
- Avoid enlarging jets unintentionally during cleaning
- When in doubt, replace the jet rather than over-drilling it
Conclusion
Understanding the relationship between Mikuni jet reference sizes and practical drill sizes can make carburetor cleaning, checking, and careful tuning more controlled. Use this chart as an approximate drill-size guide, verify the exact size needed before modifying any jet, and choose the drill set that best matches the range of sizes you need.