How To Inspect The Cylinder On Your 97-01 Honda CR250
The Tools You Will Need
- Plastic Scraper
- Soft Brush
- Shop Towels
- Mechanics Straight Edge
- Feeler Gauges
- Bore Gauges
- Calipers
- Emery Paper
- WD40
- Plastic Wrap
Pre-Service Notes
- I recommend opening the Service & Torque Specs in a new tab for easy reference.
- If you need parts and tools, make sure to buy them here!
- Pictures with captions are after the steps below.
- If you need any help don’t hesitate to ask!
Clean Your Cylinder
- 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.
- If you have a seized alignment dowel, the only thing you can do is use PB blaster 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.
- You can also tell visually. This is a cylinder from an air-cooled ATV, and you can see a distinct difference in color between the cylinder wall and the cylinder body.
- With your cylinder cleaned and deglazed, inspect the water jackets, transfer ports, and exhaust valve sub-chamber for obstruction, wear, or damage.
- Clean the mating surface on the crankcase with a plastic scraper.
- Check the surface for smoothness, and correct any pits or burs.
- Check the mounting studs for tightness and thread condition.
- If you find a loose stud, re-torque it along with the others when the cylinder is back on the bike.
Related: How to service the reed valve on your 1997-2001 Honda CR250.
Inspect Mating Surfaces For Warp
- Lay your straight edge against 2 adjacent studs, and try to fit a feeler gauge underneath.
- Record any found gaps.
- If you find any gaps, double-check the surface for smoothness and try again.
- The warp limit for the cylinder is two thousandths (0.002) of an inch.
- If your cylinder is out of spec, It will need to be reconditioned at a machine shop.
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 from front to back and side to side.
- Locations C and D can only be measured side to side, and the bottom can only be measured front to back.
- Measure, then re-measure, and record all measurements for later.
Prep Your Cylinder For Assembly
- Wash your cylinder is hot soapy water with a cylinder brush, then dry with compressed air.
- 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.
← Previous Step – Part 6: Cylinder Head Inspection
Next Step – Part 8: Exhaust Valve Inspection →
Keep Your ’97-’01 CR250 Running Right!
- Service Specification
- Clutch Replacement
- Carburetor Service
- Engine Top End
- Engine Bottom End
- Brakes
- Exhaust
- Front Suspension
- Rear Suspension
- Wheels & Tires
- Kickstarter Inspection
- External Shift Linkage
