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

Nov 16, 2018

107

How To Inspect The Cylinder Head On Your 97-01 Honda CR250

The Tools You Will Need

Pre-Service Notes

Clean the entire head with parts cleaner and a soft brush.
Clean the cylinder head mounting surface with a plastic scraper.
If 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.
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, 1000th of an inch could take your head out of spec.
Gently run your spark plug thread follower all the way through the spark plug hole to correct any potential misalignment.
If your threads are stripped out and your follower cannot correct them, you will need to install a Helicoil.

Lay your straight edge across two adjacent mounting holes, and try to fit your feeler gauge underneath.
If 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 two thousandths (0.002) of an 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.
Stop and measure your clearance 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.
Finally, check the hanger plates for damage.
If the plates are bent, or the holes are elongated, they need to be replaced.
These have some dents on the top, but they are still straight with round holes.

Keep Your ’97-’01 CR250 Running Right!