Fork Oil Level Guide
Fork oil grade and level specs for common motorcycles, plus a guide to what oil height and viscosity do to handling feel.
How to Set Fork Oil Level
- 1Drain old oil completely. Pump forks several times to purge all old oil.
- 2Pour measured volume of new oil into each leg (volume method). OR fill until level is correct (level method).
- 3For level method: fully compress fork, remove spring. Let oil settle 5 minutes.
- 4Measure from the top of the inner tube (fork fully compressed) to the oil surface.
- 5Add or remove oil until the measured level matches spec. Refit spring and close cap.
What Oil Level Does (Air Gap)
Level measured from top of fork tube, fork fully compressed, spring removed
Lower (more air gap)
Softer feel in last 1/3 of travel, more progressive bottom-out
→ Rider wants a softer, more plush feel on chop
Stock level
Balanced — designed-in air spring curve
→ Starting point; stock spec for most bikes
Higher (less air gap)
Firmer, more resistance near bottom, less dive, better support
→ Track use, heavy braking, bottoming prevention
Oil Viscosity Guide
| Grade | Feel / Application |
|---|---|
| 2.5W / 3W | Softest, fastest rebound. Reduced friction — track use. Race prepped forks, lightweight riders |
| 5W | Responsive, quick rebound. Stock on many sport forks. Sport / MX forks, most Yamaha and KTM |
| 7.5W | Balanced — good all-around street and light trail. General purpose, mid-weight bikes |
| 10W | Slightly slower rebound, more damped. Stock on many street bikes. Honda / Suzuki sport bikes, street use |
| 15W | High damping, slow rebound. Good for heavy bikes or aggressive riding. Heavy bikes, sidecar rigs, very aggressive riders |
| 20W | Maximum damping. Usually too thick for most bikes. Specialized applications only |
Fork Oil Specs by Bike
| Bike | Grade | Vol / leg |
|---|---|---|
Yamaha R6 (2006+) KYB 41mm USD | 5W or 01 | 444 mL |
Yamaha R1 (2004–2014) KYB 43mm USD | 5W or 01 | 490 mL |
Honda CBR600RR (2007+) Showa 41mm USD | 10W | 413 mL |
Honda CBR1000RR (2008–2016) Showa 43mm USD | 10W | 445 mL |
Kawasaki ZX-6R (2009+) KYB 41mm USD | 5W | 478 mL |
Kawasaki ZX-10R (2011+) Showa 43mm USD | 5W | 496 mL |
Suzuki GSX-R600/750 (K6+) Showa 41mm USD | 10W or KHL15 | 493 mL |
Suzuki GSX-R1000 (K5–K8) Showa 43mm USD | 10W or KHL15 | 500 mL |
KTM 300 EXC / XC-W WP Xplor 48mm | 5W or WP 7.5W | 350 mL |
Honda CRF450R (2017+) Showa A-Kit 49mm | 5W | 440 mL |
Yamaha WR450F / YZ450F KYB 48mm USD | 01 or 5W | 450 mL |
BMW R1250GS (2019+) Telelever (no fork oil) | N/A | N/A |
Harley-Davidson (Sportster) 39mm RSD | Type E | 275 mL |
Notes
• Always verify specs in your bike's factory service manual — specs vary by model year.
• Fork oil degrades over time. Change every 2 years or 10,000 miles on street bikes.
• Never mix fork oil grades or brands — drain completely before refilling.
• Use the volume method for consistency; use the level method for tuning air gap.