1997-2001 Honda CR250 – Top End Service – Part 6: Cylinder Head Inspection

How To Inspect The Cylinder Head On Your 1997 – 2001 Honda CR250.

1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head InspectionThe Tools You Will Need Are:

  • Plastic Scraper
  • Soft Brush
  • Shop Towels
  • Spark Plug Thread Follower
  • Metal Lubricant/Oil
  • Mechanics Straight Edge
  • Feeler Gauges
  • Emery Paper
  • WD40
  • Plastic Wrap

If you don’t have them yet, you can get a set of Feeler Gauges HERE, and your or a Machinist Straight Edge HERE.

Click Here To Open The Top End Specifications Table In A New Window

Cylinder Head Cleaning

Clean the entire head with parts cleaner and a soft brush. Clean the cylinder head mounting surface with a plastic scraper.1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - Clean1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - Wipe CleanIf you have carbon build up in the combustion chamber, soak it in parts cleaner, then gently scrub it off with a scouring pad.

Clean the spark plug threads buy threading a rolled up shop towel through the hole.

1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - Clean Spark Plug Hole With the surfaced cleaned, inspect for any signs of obvious wear or damage.

Check the water jackets are free of obstruction, and the mating surface is smooth.

You can smooth out small burs and pits with 600 grit emery paper, but be very careful, 0.001 inch could take your head out of spec.

Lubricate the spark plug hole, and gently run your spark plug thread follower all the way through the spark plug hole to correct any potential misalignment.1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - Spark Plug Thread FollowerIf your threads are stripped out and your follower cannot correct them, you will need to install a Helicoil (link to RockMountainATVMC.com).

Inspect Cylinder Head Warp

Lay your straight edge across two adjacent mounting holes, and try to fit your feeler gauge underneath.

1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - Head Warp Check 1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - Head Warp Check 2If you find any gaps, double check the head for smoothness, and try again.

If the gap still exists, record the measurement.

Repeat this measurement around the head.

The warp limit for your cylinder head is 0.002 inch.

You may be able to bring your head into spec with a sheet of 600 grit emery paper.

Tape the emery paper to a sheet of glass, and dampen with water.

Run your cylinder head in a figure eight motion against the paper, using light pressure.1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - Emery PaperStop and measure your cylinder head warp every 3 passes.

If you cannot bring your head back to spec, you will need to take it to a machine shop.

Clean your cylinder head with HOT soapy water, and rinse thoroughly.

Dry with compressed air and double check the mating surface for smoothness.

If everything looks good, apply a light coat of WD-40 to avoid oxidation, and wrap your cylinder head in plastic wrap to avoid contaminants until you are ready for assembly.1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - WD40 and Plastic WrapCylinder Head Hanger Plates

Finally, check the hanger plates for damage.1997 - 2001 Honda CR250 - Top End Service - Part 6 - Cylinder Head Inspection - Inspect Hanger PlatesIf the plates are bent, or the holes are elongated, they will not support the cylinder properly, and they need to be replaced.

These have some dents on the top, but they are still straight with round holes.

Part 5: Piston Inspection
Part 7: Cylinder Inspection
1997 - 2001 Honda CR250 - Top End Service - Part 5 - Piston Inspection1997 - 2001 Honda CR250 - Top End Service - Part 7 - Cylinder Inspection

 

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