How To Remove And Disassemble The Crankcase On Your 97-01 Honda CR250
- 8mm Socket
- 14mm Socket
- 22mm Socket
- Wood Blocks
- Big Hammer
- Plastic Scraper
- Flat Razor
- Dremel with Sanding Disc
- Paper Towels
- Safety Glasses
The only specialty tool you will need is a case splitter, and you can get one through our partners here.
- Put your bike on a sturdy stand and drain oil and coolant.
- I recommend opening the Bottom End Service Specifications 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!
Bottom End Removal
- You have three bolts attaching the bottom end to the frame, two mounting bolts, and the swingarm pivot shaft.
- Start by removing the swingarm pivot shaft first, because I have never had one come out easy.
- You may find yourself with a seized shaft. The only thing you can do is hose it down with anti-seize, then wait, then hit the bolt with the biggest hammer you have, then repeat as needed.
- You will need a new pivot bolt, but they are not too expensive.
Remove the two lower mounting bolts, and keep track of their direction for install.
- Remove the engine from the frame. The swingarm may be resting on the rear of the case, so lift the front end first and give it a jiggle. But do not lift the case by the crankshaft like this impatient idiot.
- With the case removed, clean and inspect the frame.
- Lay your crankcase on your blocks with the left side facing up. Loosen the 11 crankcase bolts in a criss-cross pattern, ¼ turn at a time until they are all loose.
- The crankcase bolts vary in length, so outline the case on cardboard or styrofoam and place your bolts accordingly.
- Assemble your crankcase splitter and attach it to the case.
- Remember to keep the splitter parallel to the case.
- Begin tightening the splitter nut.
- After every turn, firmly tap the case seam with a rubber mallet. Make sure to check the case gap frequently if the case is separating unevenly, back out the splitter nut to remove pressure from the case. I had to tap aggressively on the front of the case where a dowel had seized.
- With the cases separated, remove the two alignment dowels, o-ring, and gasket material.
- Take every precaution you can when handling the transmission. Keep it oiled, wrapped, and clean at all times.
- Remove the two shift fork shafts, followed by the shift drum, and the shift forks.
- Remove the main shaft and countershaft as a unit, keeping the gears meshed.
- Wrap the assemblies in a towel and set aside.
- Flip the right crankcase, so the outside is facing up, and place a layer of towels under the crankshaft. Attach the crankcase splitter with WASHERS… and press the crankshaft out of the case.
- Again, remember to keep the splitter parallel to the case.
- If your main shaft bearing comes out with the crankshaft, you will need to use your bearing splitter to remove the bearing from the shaft.
Clean & Inspect
- The mating surfaces must be spotless and smooth to ensure a tight seal. Start by removing all gasket material from the mating surfaces with part cleaner and a plastic scraper. With the big pieces gone, move onto the tough spots with a flat razor, taking extra care not to gouge the surface.
- With all the gasket material gone, give the surface a once over with a fine grit sanding disk. If you don’t have a Dremel, 600 grit emery paper will work just fine. You want to have a smooth almost mirror finish when you are done.
- This case has quite a few rough spots leftover from casting. I have the equipment and the time, so I am going to smooth those out while I have to opportunity.
- Remove the oil seals from the crankcase. Make sure to use a towel to protect the body.
- Thoroughly wash the crankcase with water and solvent. Thoroughly dry with compressed air, and coat with a layer of WD40.
- With your case clean and shiny, check for any unusual wear or cracking. Inspect the crankshaft for cracks, rubbing, pitting and heat damage.
- Check the connecting rod for play.
- If something doesn’t look right, take your crankshaft to a machine shop or dealership to check the runout and connecting rod radial clearance.
- This crankshaft is nonrepairable, and if it is out of spec, you need to replace it entirely.
Keep Your ’97-’01 CR250 Running Right!
- Service Specification
- Clutch Replacement
- Carburetor Service
- Engine Top End
- Engine Bottom End
- Front Suspension
- Rear Suspension
- Wheels & Tires
- Kickstarter Inspection
- External Shift Linkage