How To Change The Crankcase Bearings And Seals On Your 1997 – 2001 Honda CR250.
These bearings are an interference fit, meaning the outside diameter of the bearings is slightly bigger than the inside diameter of the bore. The only way you can remove and install these bearings is by changing their sizes. Interference fit means you will need to freeze your new bearings to contract them, and heat the case halves in the oven to expand the bores.
Do not try to remove and install these bearings with a torch or force. The uneven temperature will compromise the metal, and force will break it. When done right, the bearings will practically remove and install themselves.
The New Parts You Will Need Are:
- Main Bearings
- Transmission Bearings
The Tools You Will Need Are:
- Baking Sheet
- Baking Sheet
- Oven Mitts
- Laser Thermometer or Water
- Bearing Drivers
- Slide Hammer (Maybe)
- Denatured Alcohol
- Safety Glasses
Before you take your case to the oven, make sure you have all the bearings you need.
For this crankcase, I am using a Hot Rods transmission bearings kit, and OEM main bearings.
If you don’t have your new bearings yet, you can buy them through our partner links!
Match your new bearings with the old ones. Keep the new ones separated by case side, because you will install them one side at a time.
The last thing to do before you bake your cases is to remove the screws and retainers in the left case, and the bolts and retainers in the right case.
Dirt Bike Bake Off!
Preheat your oven to 350 degrees Fahrenheit, or 180 degrees Celsius, if you’re fancy,
The heat will let you know if you cleaned your case well enough. Any residue on your case is about to turn to smoke inside your house, so you might want to double check your work.
Place your case half on your blocks, bearing side down, and place it in the oven for about 10 minutes.
The case wall is thicker at the crank, meaning it will take the longest to heat up, so that is where you want to measure your temperature.
The ideal temperature to work at is 250 degrees Fahrenheit, or 120 degrees Celsius if ya nasty.
The accurate way to measure the temperature is with a laser thermometer, but if you don’t have one, flick some water on the case, if it sizzles and evaporates immediately, you should be good.
Remove the case and tap the bearings. If they don’t fall out with a few taps, return the case to the oven and wait another 5 minutes.
After you remove the bearings, let the cases cool and clean the bearings bores with denatured alcohol.
To install the new frozen bearings, reheat your case halves, and drop them into place. If they don’t sit flush, or all the way, lightly tap them until they do.
Repeat with the other half.
After your cases cool down, install the retainers and screws in the left case, and the retainers and bolts in the right case.
While your crankcase is disassembled, consider changing the clutch lifter bearings.
Removing these bearings can be a hassle because of their shape, and placement.
Usually, you can slide the bearings out with a pick, but I had to use a slide hammer on these.
Install the bearings with a socket, then grease and install the new seal.
|Part 2: Transmission||Part 4: Assembly & Install|
Keep Your ’97-’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