Keihin Carburetor Jet Size Chart & Drill Size Guide
This guide provides a practical reference for Keihin carburetor jet sizes and drill sizes commonly used for cleaning, checking, and careful tuning work. Keihin carburetors include many different models and jet types, so this guide should be used as a practical drill-size reference rather than a guaranteed manufacturer specification.
About Keihin Carburetors
Keihin carburetors are widely used on motorcycles, ATVs, scooters, dirt bikes, go-karts, powersports equipment, and related small-engine and performance applications. Common Keihin-style carburetor families include CV, CVK, FCR, PE, PJ, PWK, PWM, PD, and related models.
Depending on the carburetor model, Keihin tuning may involve main jets, pilot jets, slow jets, needles, needle jets, and other calibrated fuel-metering components. Keihin jet sizes are commonly identified by reference numbers, but the correct jetting depends on the exact carburetor model, engine, exhaust, intake, elevation, and tuning goal. Always verify the specific jet type and application before cleaning, checking, or modifying a jet.
Which Drill Set Is Right for Keihin Jet Work?
For Keihin carburetor jet checking, cleaning, and careful sizing work, choose a drill set based on the jet type and diameter range you expect to work with.
Best Starting Point for Many Keihin Jet Jobs: 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 Numbered-Drill 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, useful when working with small, brittle carbide drills and smaller jet ranges.
Working on Larger Jets or Multiple Carburetor Brands?
If you work on larger carburetor jets, Holley-style ranges, Rochester/Quadrajet applications, Weber main jets, 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.
Keihin Jet Size Chart & Drill Size Reference
Many Keihin jet references use numbered or metric-style sizing depending on the jet type and carburetor family. A size such as 100 is commonly treated as approximately 1.00 mm for practical drill-size comparison, but Keihin jet numbering and actual fuel flow can vary by jet type, carburetor model, and manufacturer reference.
The Nearest Drill Size Reference column shows the closest practical drill size or drill range for comparison. It is meant for checking and reference only; always verify the actual jet and carburetor application before modifying anything.
| Jet Reference Size | Metric Reference | Approx. Inches | Nearest Drill Size Reference |
|---|---|---|---|
| 35 | 0.35 mm | 0.0138" | #80 range |
| 38 | 0.38 mm | 0.0150" | #79 / #78 range |
| 40 | 0.40 mm | 0.0157" | #78 |
| 42 | 0.42 mm | 0.0165" | #77 range |
| 45 | 0.45 mm | 0.0177" | #77 range |
| 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 |
| 90 | 0.90 mm | 0.0354" | #65 |
| 100 | 1.00 mm | 0.0394" | #61 |
| 110 | 1.10 mm | 0.0433" | #57 |
| 120 | 1.20 mm | 0.0472" | #56 / metric drill range |
| 130 | 1.30 mm | 0.0512" | #55 range |
| 140 | 1.40 mm | 0.0551" | #54 |
| 150 | 1.50 mm | 0.0591" | #53 |
| 160 | 1.60 mm | 0.0630" | 1.60 mm / #52 range |
| 170 | 1.70 mm | 0.0669" | #51 range |
| 180 | 1.80 mm | 0.0709" | 1.80 mm range |
| 200 | 2.00 mm | 0.0787" | 2.00 mm range |
Note: This chart is an approximate drill-size reference. It should not be treated as an official Keihin specification or a guaranteed fuel-flow conversion.
Using Drill Sizes for Keihin 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. Keihin jetting may involve several different jet types, so make sure you are working with the correct jet before using a drill.
Practical Drill Size Range for Keihin Jets
Many Keihin jet references fall within small metric-style carburetor jet ranges. Pilot and slow jets may fall into the smaller ranges covered by selected-size and numbered drill sets, while larger main jets may require larger metric drill sizes depending on the carburetor model and application.
For this reason, the 20-piece selected-size set may be a practical starting point for many smaller Keihin jet checking and cleaning jobs, while larger Keihin main jet work may require comparing the full carburetor jet drill set collection before ordering.
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
- Confirm whether you are working with a main jet, pilot jet, slow jet, needle jet, or another calibrated component
- 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 Keihin jet references 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 jet type and size before modifying anything, and choose the drill set that best matches the range of sizes you need.