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.
Keihin Carburetor Jet Drill Sets
For Keihin carburetor work, choose the set that matches the jet range you expect to work with.
Pilot & Slow Jets — 10 Pc Set
Selected metric sizes from 0.35 mm through 0.80 mm for smaller Keihin pilot and slow jet work.
Main Jets — 20 Pc Set
Selected metric sizes from 0.85 mm through 1.80 mm for Keihin main jet work.
Complete Keihin Range — 30 Pc Set
Combines the pilot/slow and main jet ranges into one assortment covering 0.35 mm through 1.80 mm in 0.05 mm increments.
Important: Keihin uses additional intermediate jet sizes in some jet series. These are selected-size assortments and are not intended to represent every Keihin jet number.
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.
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 Metric Reference and Approx. Inches columns show the reference diameter for comparison. The final column shows a nearby numbered or fractional drill equivalent when useful, but it may not be an exact dimensional match.
Only need an individual drill size?
0.35–0.90 mm: Shop .0039"–.036" individual drills →
1.00–2.00 mm: Shop .037"–.0787" individual drills →
How to use this chart: If you need a drill matching the reference diameter, use the Metric Reference or Approx. Inches value. The final column is only an approximate numbered or fractional drill comparison and may differ slightly from the reference diameter.
| Jet Reference Size | Metric Reference | Approx. Inches | Approx. Number / Fractional Drill Equivalent |
|---|---|---|---|
| 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.
Choosing the Right Keihin Drill Set
If you know which type of jet you are working with, the three Keihin-specific sets provide a simpler way to choose the appropriate drill range:
- Pilot and slow jet work: use the 10 Pc Keihin Pilot & Slow Jet Set covering 0.35–0.80 mm.
- Main jet work: use the 20 Pc Keihin Main Jet Set covering 0.85–1.80 mm.
- Working across both ranges: use the 30 Pc Complete Keihin Set covering 0.35–1.80 mm.
If the exact diameter you need is not included in one of the selected-size sets, use the individual drill links above to look for a closer size.
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.
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 Keihin drill set that best matches the range of sizes you need.