How To Inspect The Cylinder On Your 1997 – 2001 Honda CR250.
The Tools You Will Need Are:
- Plastic Scraper
- Soft Brush
- Shop Towels
- Mechanics Straight Edge
- Feeler Gauges
- Bore Gauges
- Emery Paper
- Plastic Wrap
If you don’t have them yet, you can get a set of Feeler Gauges HERE, a set of Bore Guages HERE, and your or a Machinist Straight Edge HERE.
Clean your cylinder as thoroughly as you can without damaging the mating surfaces or bore. Remove all gasket material with a plastic scraper, and smooth any pits or burs with 600 grit emery paper.Check the cylinder head mounting studs.
If you have a seized alignment dowel, the only thing you can do is use PB Blaster (or whatever penetrating oil you prefer) and be patient, otherwise you will need to go to a machine shop to have it removed.
If carbon build up is present in the bore, it will need to be deglazed. There are two methods of deglazing, depending on your cylinder wall material.
Stock, this is an aluminum cylinder with Nikasil plating, and can by carefully deglazed with a scouring pad.
However, your cylinder may have been bored out and fitted with an iron sleeve, which can be deglazed with a ball hone.
The definite way to tell is using a magnet. If it sticks, it’s sleeved.
With your cylinder cleaned and deglazed, inspect the water jackets, transfer ports, and exhaust valve sub chamber for obstruction, wear, or damage.
Inspect Cylinder Mating Surfaces For Warp
If you find any gaps, double check the surface for smoothness and try again.
The warp limit for the cylinder is 0.002 inch.
If your cylinder is out of spec, It will need to be reconditioned at a machine shop.
Cylinder Bore Inspection
Before you measure the cylinder bore, visually inspect it.
If you feel a defined lip at the top of the cylinder bore where the piston rings stop, or if the plating is chipped or damaged around the intake, exhaust, and transfer ports, it needs to be replated.
This cylinder is in excellent condition considering the unusual wear on the piston. The intake side is slightly marked, but is still smooth, so I’m comfortable with reusing it as long as it’s within spec.
Draw out a chart to keep track of your measurements.
Measure your cylinder in five locations at 10, 30, 80, 100, and 130mm from the top of the cylinder.
Label the locations A, B, C, D, and Bottom.
Locations A and B can be measured front to back and side to side.
Apply a thin coat of WD-40 to the cylinder walls to inhibit oxidation, and wrap your cylinder in plastic wrap until you are ready for assembly.
|Part 6: Cylinder Head Inspection||Part 8: Exhaust Valve Inspection|
Keep Your ’99-’01 CR250 Running Right!
- Service Specification
- Clutch Replacement
- Carburetor Service
- Engine Top End
- Front Fork Maintenance
- Rear Shock Rebuild
- Wheels & Tires
- Kickstarter Inspection
- External Shift Linkage