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Checking the Valve Clearance on a CRF450R

The owner's manual suggesting checking the valve clearance every 6 races or every 15 hours. I can't say I check my that often but I do check it frequently. This especially important when your bike is new to make sure the valves are in spec and not headed for damage. This how-to article will walk you through the steps so you can do this yourself. Even, if you're not a weekend wrencher you should be able to check your valves following these simple steps.

Since you'll be drain fuel from the fuel line make sure you are working in a well ventilated area that is void of any ignition source. It's always a good idea to have a clean bike whenever you are wrenching. In this case, it is more than a good idea, it's mandatory. You'll be removing the valve cover and any dirt that would fall into this area could cause significant engine damage.

Tools Needed

  • 8mm and 10mm socket
  • Extension or t-handle
  • Torque wrench
  • 10mm allen wrench
  • Pliers

Step-By-Step Instructions

  1. Remove seat (10mm socket ) and shrouds (8mm socket)
  2. Turn off the petcock and remove the fuel line, at the petcock, that connects from the petcock to the carb. Drain the fuel from this fuel line. Move it out of the way and downward so debris can't fall into it.
  3. Remove the bolt that holds the petcock.
  4. Remove fuel tank by removing bolt at top (8mm socket) and retainer strap at bottom.
  5. With the fuel tank removed, clean the valve cover and surrounding area. Make sure to clean the cables and wires in the area. There should be no dirt or debris that could fall into the top of the cylinder head once the valve cover is removed.
  6. While you've got the fuel tank off this is a great time to install the Applied Racing Crankcase Vent Kit. You can see the review and installation tip for this kit in our the Product Review area.
  7. Remove the spark plug cap and crankcase breather tube.
  8. Remove the three valve cover bolts (10mm socket).
  9. Remove the crankcase hole cap and o-ring (10mm allen wrench).
  10. Turn the crankshaft clockwise to align the punch mark on the primary drive gear with the index mark on the right crankcase cover. YOu can turn the crankcase by using the kick starter. You may find it easier to turn the crank by removing the spark plug to eliminate cylinder compression. Make sure the cylinder is at Top Dead Center (TDC) on the compression stroke. This can be found when the cam lobes are facing the rear of the bike and the punch mark and timing marks are aligned.
  11. Measure the intake valves clearance by sliding the feeler gauge down between the cam lobes and valve lifter. The valve clearance should be 0.16+/-0.03mm (0.006-/+0.001 in.). Record your findings in your maintenance log.
  12. Measure the exhaust valves clearance by inserting a feeler gauge between the rocker arm and shim bucket. You may need to apply some pressure to the exhaust rocker to insert the feeler gauge under the rocker arm. The valve clearance should be 0.28mm-/+0.03 (0.011-/+0.001 in.). Record your findings in your maintenance log.
  13. If any of the valves are not within specifications then you'll need to shim them. Shimming will be handled in a how-to in the future.
  14. While you've got the cover off, it's a great time to inspect the valve train for wear or damage. Using the kick starter slowly turn the crank while inspecting the cam surfaces and timing chain and sprocket.
  15. Clean and inspect the rubber o-ring on the crankshaft hole cap and install (10mm allen wrench)
  16. Clean and inspect the gasket on the valve cover. Install the cover paying special attention to the area around the spark plug housing. If this area is damage oil will leak into the spark plug area and eventually will drain out the water drain hole on the right side of the cylinder.
  17. Torque the three valve cover bolts to 7lbf-ft. Do not be tempted to over tighten these bolts. More is not better and will only lead to damaging the valve cover and or causing oil to leak.
  18. Install the tank, petcock, and fuel line.
  19. Install the radiator shrouds and seat.

That's it! Famous last words I know. However, don't be intimidated if you've never done this before. Read this a couple of times, read your owners manual and go for it!

CRF's Only "How-To" By CRF's Only Staff Writer, June 2005
 

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