How to Check Valve Clearances on a Honda CRF250R

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Regularly checking valve clearances on your modern 4-stroke racing machine is critical to keeping you and your bike competitive. Because of their incredible power output and insane RPM capabilities, these engines need to be maintained regularly and properly. More often then not, such a simple procedure as checking valve clearances is overlooked, and can easily lead to a major engine (and wallet) disaster. Ensuring that your valve clearances are within their operating limits is critical for the longevity and performance of your engine.

Steps

1. 1
   Start by removing the seat, gas tank, and rad shroud plastics.

   
   
2. 2
   With some water and a shop towel wash the area around the cylinder head clean.
3. 3
   Take out the spark plug cap and set it aside.
4. 4
   Remove the 2 (10mm) rocker cover bolts.
5. 5
   Remove the spark plug.
6. 6
   Remove the crankshaft hole cap from the crankcase.
7. 7
   

   Find top dead centre by turning the engine over until the punch mark on the crankshaft lines up with the arrow on the crankcase (see picture).
   Find top dead centre by turning the engine over until the punch mark on the crankshaft lines up with the arrow on the crankcase (see picture). To turn over the engine, slowly using the kickstarter by hand and/or using an allen key on the crankshaft will work.
8. 8
   

   Once TDC is found, find the specified feeler gauge thickness for intake valves (refer to owner's manual).
   Once TDC is found, find the specified feeler gauge thickness for intake valves (refer to owner's manual)
9. 9
   

   Using the right feeler gauge thickness for the intake valves, slide it down on the front facing side of the cam lobe.
   Using the right feeler gauge thickness for the intake valves, slide it down on the front facing side of the cam lobe. It will have to be bent slightly to get it fit between the lobe and the top of the valve bucket.
10. 10
    Slide the feeler gauge up and down through the gap a couple of times to confirm that it can move freely, and that the valve is within spec. Repeat step for both intake valves.
11. 11
    Select the optimal exhaust feeler gauge thickness as indicated in the owner's manual.
12. 12
    

    Using the proper feeler gauge thickness for the exhaust valves, horizontally slide it beneath rocker arm tip and the top of the exhaust valve.
    Using the proper feeler gauge thickness for the exhaust valves, horizontally slide it beneath rocker arm tip and the top of the exhaust valve.
13. 13
    Slide the feeler gauge back and fourth through to confirm that it can move freely, and that the valve is within spec. Repeat step for both exhaust valves.
14. 14
    Re-install rocker cover and torque the 2 bolts to spec. (indicated in manual)
15. 15
    Re-install crankcase hole cover, sparkplug and sparkplug cap.
16. 16
    Re-install gas tank, plastics and seat.
17. 17
    Done!

    
    

Video

Warnings

• Make sure your workspace is clean! Even minor dirt and debris falling into the cylinder head assembly can cause some major problems!
• If you cannot get the intended feeler guage into any given gap you are measuring, it means that valve has tightened and is now out of specification. You can either re-shim it to spec (which will only last so long), or you will have to get a cylinder head re-build.

Things You'll Need

• Torque Wrench
• Ratchet
• 10mm Socket
• 8mm Socket
• Spark Plug Socket
• Feeler Gauges
• Owners Manual
• Metric Allen Key Set
• Flashlight
• Rag
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