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.
Need Drill Bits for Mikuni Jet Work?
If you are using this chart to clean, check, or carefully size carburetor jets, choose a drill set based on the diameter range you need.
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General Mikuni and small carburetor jet work: choose a smaller carburetor jet drill set if you only need common numbered-drill sizes for checking, cleaning, or careful tuning.
Compare carburetor jet drill sets → -
Need 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.
View carburetor jet drill sets → -
Need a larger range? compare all carburetor jet drill sets to find the range that best matches your carburetor work.
Compare available jet drill sets →
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 or partially blocked jets
- Checking approximate jet size
- Comparing jet openings to known drill diameters
- 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 below 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 set may be enough for common cleaning, checking, or tuning work.
- 20-piece carburetor set: useful for smaller common carburetor jet work where you only need selected sizes.
- 25-piece carburetor set: covers a broader #75–#51 range for general carburetor jet checking, cleaning, and careful tuning.
- D7 50-piece #80–#56 set: includes 25 drill sizes with two drills per size, useful when you want backup drills in each size.
- HS1 50-piece Holley-focused set: covers a larger .040"–.125" range and may be useful when larger jet reference sizes are needed.
- Ford Model A Zenith set: selected for Ford Model A Zenith carburetor jet work.
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.