Honda CRF150F & CRF150R Technical Specs, Torque & Service Bible 

How often should I change the oil on my CRF150? For the CRF150F, it is recommended to change the oil every 20–30 hours of trail riding. For the high-performance CRF150R, service intervals are much tighter, often requiring an oil change every 15 hours or after every few races to protect the high-revving engine components.

What is the correct spark plug for the Honda CRF150? The CRF150F typically uses an NGK DPR8EA-9. The CRF150R requires a higher-heat range plug, usually the NGK R0452A-9 or NGK IMR9C-9H. Always check your specific year’s manual to confirm the gap settings.

What is the difference between the CRF150F and the CRF150R? The CRF150F is an air-cooled, trail-oriented bike built for durability and ease of maintenance. The CRF150R is a liquid-cooled, "Unicam" race machine designed for motocross competition, featuring higher compression and more advanced suspension.

What is the valve clearance for the CRF150R? To maintain peak performance, the intake valves should typically be set to 0.16mm (± 0.03mm) and exhaust valves to 0.26mm (± 0.03mm). Regular inspection is critical for the Unicam engine design.

Honda CRF150F (Trail)

Honda CRF150R (Race)

Engine Type

Air-cooled, Single-cylinder

Liquid-cooled, Unicam Single

Displacement

149cc

149.7cc

Bore & Stroke

57.3mm x 57.8mm

66.0mm x 43.7mm

Compression Ratio

9.5:1

11.7:1

Fuel System

24mm Piston-valve Carb

32mm Keihin FCR Carb

Transmission

5-Speed

5-Speed

Front Suspension

35mm leading-axle fork

37mm inverted Showa fork

Rear Suspension

Pro-Link Showa single shock

Pro-Link Showa single shock

Dry Weight

~101 kg (223 lbs)

~80 kg (176 lbs)

General Maintenance

Q: How often should I change the oil on my CRF150?

• A: For the CRF150R (Race), change the oil every 15 hours of riding (or sooner if racing hard). For the CRF150F (Trail), every 20–30 hours is standard. Always check your air filter at the same time; a clogged filter is the #1 cause of poor performance.

Q: What are the valve clearance specs?

• A: * CRF150F (Cold): Intake: 0.08mm / Exhaust: 0.12mm.

  • CRF150R (Cold): Intake: 0.16mm ± 0.03mm / Exhaust: 0.26mm ± 0.03mm.

  • Tip: If your bike is getting hard to start when cold, tight intake valves are usually the culprit.

CRF150R (Liquid-Cooled Performance)

Q: Why is my CRF150R so hard to start when the engine is hot?

• A: This is a common "heat soak" issue. First, ensure you are using the Hot Start lever (the small silver lever above the clutch). If that doesn't work, check your pilot jet for clogs or inspect your valve clearances—tight valves expand when hot and lose compression.

Q: My CRF150R is spitting coolant out of the overflow. Is it overheating?

• A: It might be. Check for mud or bent fins in the radiators. If the radiators are clear, replace your radiator cap; a weak spring in the cap won't hold pressure, causing the bike to "boil over" prematurely.

CRF150F (Air-Cooled Trail)

Q: My bike only runs with the choke on. What’s wrong?

• A: Your pilot jet is likely clogged with old fuel varnish. The CRF150F has very small carb passages. Removing the bowl and cleaning the jets with compressed air and carb cleaner usually fixes this "lean" condition.

Q: Why does my transmission feel "notchy" or hard to shift?

• A: Check your oil level first. If the oil is fresh, check your clutch cable adjustment. If there is too much slack, the clutch isn't fully disengaging, making gear changes feel rough.

Troubleshooting "Bogging"

Q: Why does my bike "bog" or stall when I whack the throttle open?

• A: * CRF150R: This is often an Accelerator Pump issue. The "O-ring mod" or adjusting the pump timing can help eliminate that 4-stroke hesitation.

  • CRF150F: Usually a sign of being too lean on the needle clip position or a dirty main jet.