97-01 Honda CR250 - Bottom End Service - Part 2: Transmission Service

Apr 23, 2019

1997-2001 Honda CR250 – Bottom End Rebuild – Part 2: Transmission Service

How To Service The Transmission On Your 97-01 Honda CR250

Inspecting your transmission is not a hard job, but it does require cleanliness, organization, notes, and math.

No matter what you find during your inspection, you WILL need three new snap rings, as the old ones will deform when you remove them.

As you go, measure the inside diameter of the gears, and the inside and outside diameters of the bushings.

Inspect every part for visible wear, like broken teeth, cracking, gouging and pitting. If anything even looks damaged, you will need to replace the part.

The Tools You Will Need

4 Long Screwdrivers
Snap Ring Pliers
Calipers
Parts Cleaner
Towels
Safety Glasses
Notepad & Pen

Let’s start with the Mainshaft.

Pre-Service Notes

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!

Transmission Mainshaft

The main shaft is the larger of the two shafts.
Disassemble the main shaft, transferring every part, in order, to a long screwdriver.
Inspect and measure each gear, washer, and bushing.
Measure the main shaft diameter at fifth gear, and inspect the splines, gears, and snap ring grooves.
Record each measurement as you go.

1 - Start With The Mainshaft — Start With The Mainshaft

2 - Transfer Gear Stack To Long Screwdriver — Transfer Gear Stack To Long Screwdriver

3 - Keep Things Organized — Keep Things Organized

Mainshaft Gear Stack Orientation

Washer
Second gear
Washer
Fourth gear and bushing
Spline washer
Snap ring
Third gear
Snap ring
Spline washer
Fifth gear
And first gear is the countershaft

4 - Inspect And Measure Countershaft Gear Stack — Inspect And Measure Countershaft Gear Stack

5 - Record All Measurements For Later — Record All Measurements For Later

Transmission Countershaft

The countershaft is the shorter of the two shafts and is disassembled from both sides.
Remove each side to a separate screwdriver, cleaning and measuring as you go.
Measure the countershaft at first, second, and third gear positions, and check the splines and snap ring grooves for damage.
Record every measurement as you go.

6 - Transfer Countershaft Gear Stack To Screwdrivers — Transfer Countershaft Gear Stack To Screwdrivers

7 - Clean And Measure Countershaft Gear Stacks — Clean And Measure Countershaft Gear Stacks

Countershaft Gears Stack – Left Side Orientation

Washer
Second gear and bushing
Washer
Fourth gear

Countershaft Gears Stack – Right Side Orientation

Washer
First gear and bushing
Washer
Fifth gear
Snap ring
Spline washer
Third gear
Washer

Clearance Calculations

You will need to calculate the clearance between the gears and their bushings and the bushings with the shaft.

Here is a link to the service specifications. In the second table, you will see the various clearances that need to be measured and calculated.

Shift Drum & Forks

Clean the shift drum, forks, and fork shafts.
Measure each forks claw thickness, inside diameter, and guide pin.
Measure the diameter of the long shift fork shaft at each end and center point.
Measure the short shift fork shaft at the center point.
Check the play of each shift fork in their respective gears.
1. Right shaft to fifth gear
2. Center shaft to third gear
3. Left shaft to fourth gear.
The forks should have a slight play in the grooves.

8 - Clean And Inspect Shift Forks, Shafts, And Drum — Clean And Inspect Shift Forks, Shafts, And Drum

9 - Measure Fork Claw, Pin, And Inside Diameter — Measure Fork Claw, Pin, And Inside Diameter

Shaft Assembly

If everything has stayed in order, all you need to do is transfer your gear stack from your screwdrivers back onto the shafts.
Make sure to use plenty of assembly lube at every contact point.
During assembly, you will need to make sure your new snap rings and washers are facing the correct direction.
Although both sides look flat, one side is slightly rounded.

Mainshaft Snap Ring And Washer Direction: (Flat Side, From Left To Right)

Washer: Left | 2nd | Washer: Right| 4th | Washer: Left | Snap Ring: Left | 3rd | Snap Ring: Left | Washer: Left | 5th | 1st

Countershaft Snap Ring And Washer Direction: (Flat Side, From Left To Right)

Washer: Left | 2nd | Washer: Right | 4th | Washer: Left | 3rd | Washer: Right | Snap Ring: Right | 5th | Washer: Right | 1st | Washer: Right