pay attention to you scooterís crank bearings, rod bearings and maybe even the
steering head bearings. But do you ever check the most important bearings on
your scooter, the final reduction and wheel bearings?
The bearings used in the Honda CH250 are relatively modern and last a long time.
However, on high-mileage scoots or ones driven in wet weather or washed with
high pressure hoses, the bearings can go out sooner than you think. In the case
of this example, a well-used CH250, the front wheel bearings were completely
shot after two years. The bearings were so worn that the wheel could flop around
about a half-inch at the rim.
Bearings have a tough life. They are precision made parts subject to large
amounts of stress and need lubrication. Typically, they have to rely on a
little grease added at the factory, maybe many years ago. When they run
or start to rust, they will heat up, wear out of round and develop excess
Most bad bearings aren't immediately obvious, though they will get worse quickly
if you ignore the first signs. Bad bearings can show up as a faint 'tick..tick'
noise as you push the scoot into the garage, or a clicking sound as you drive.
This may even show up as an intermittent noise. You can feel a grittiness in the
bearings when you turn them by hand when the wheel is off for a tire change.
Usually, bad bearings will not turn as easily as good ones and will feel 'lumpy'
as you turn them, instead of turning smoothly.
Most Honda CH250s use caged ball bearings with oil seals protecting them. The
final reduction case, or transmission, has numerous bearings and gears which
transfer the torque from the engine to the rear wheel. Letís examine the final
The final reduction cover holds the drive shaft with a bearing and seal. This 50
mm bearing (91005-KS4-003), although exposed to final reduction gear case oil
for lubrication, receives the brunt of the torque from the belt drive and the
weight of the clutch assembly which is 8 lbs. Compound that with neglectful
final reduction oil changes, this bearing is most susceptible for failure.
Because of this, itís not unusual to see this bearing fail while the other two
bearings in the reduction cover look new.
To replace this bearing, remove the final reduction cover, press the drive shaft
out of the final reduction cover with the bearing, then remove the bearing with
a bearing puller from the drive shaft. Reinstall in reverse.
The second most troublesome bearing in the final reduction is the 52 mm final
shaft bearing. Think about this, the final shaft drives the rear wheel. It is
supported by a wheel bearing in the swing arm assembly. The rear wheel holds
most of the scooter weight including the operator. Add a passenger, and that
bearing takes a beating.
The final shaft bearing (96150-62053-10) is pressed into the left crankcase. The
final shaft and final gear are removed by removing the swing arm and rear tire.
A gentle hammer from the muffler side removes the shaft from the final
chamber Tip: Anytime you examine a shaft which rides within a bearing and the
inside race of the bearing or outside shaft which the bearing rides is brown,
that indicates bearing turning resistance, or scoring, indicative of bearing
failure. The final shaft bearing is removed by hammering it out of the case from
the muffler side with a bearing driver. The replacement bearing is installed
with a 52 mm driver attachment.
The third most neglected bearing is the 47 mm swing arm bearing or rear wheel
bearing. This bearing (96150-63030-10) has two oil seals (91259-KM1-003) on each
side. Since you already have the rear wheel off and the swing arm assembly,
replace the bearing. The swing arm bearing partially supports the load of the
scooter on the final shaft. It is easily pressed out of the swing arm and
replacement will avoid future problems.
Some tips about bearing removal procedures: Ball bearings are usually a press-fit
into the assembly with a slight interference fit between the assembly and the
outer race. To remove them you may need to heat up the assembly around the
bearing. While you can drive out the old bearings without heat if you use enough
force, heating the bearing assembly to expand it makes bearing removal easier
and causes less damage to the seating surface. Beware of using too much
heat which may cause metal distortion. A propane torch or industrial heat gun
(basically a huge 5000 watt blow-drier) works well to heat up steel or aluminum.
When the assembly is warm (the hottest it should get is hot enough to touch for
a moment without burning yourself) you can drive the bearing out with a driver.
Bearings have an inner and outer race. Once you start hammering on the inner
race the bearing is shot--ball bearings can't take sharp side loads and will get
flat spots, ruining it.
Inserting the new bearing is the reverse of removing the old. You can put the
new bearing in the freezer while preparing to heat up the bearing assembly to
receive it. Heat the assembly until water sizzles when a few drops are sprinkled
on it. Then quickly drop the new bearing in and seat them with a driver. If you
don't have a bearing or seal driver, use a socket or piece of pipe of the same
diameter as the outer race to seat the bearing.
Pounding on the inner race will damage the bearing, requiring you to remove it
again soon. Make sure that the bearing starts square to the assembly and doesn't
get cocked sideways as you drive it in.
Bearings are normally installed with the writing (on the edges of the
towards the outside of the wheel, and should be seated fully against a shoulder
in the bearing cavity. Best to check the manual if you didn't check the bearing
when you removed it.
Have you ever noticed when you misplace something, itís always in the last
place you look? So, what does this have to do with bearing noise? Easy--a
systematic elimination of bearing components will leave the bearing noise in the
last place you look!
Hereís what I do in this application: Remove the left side cover. Isolate the
variator from the clutch by removing it and the belt. Spin the clutch assembly
on the drive shaft. The clutch assembly has an inner and outer bearing. Bad
bearings will elicit a grinding noise. Remove the clutch assembly and check each
bearing by turning it with your finger.
Next, remove the final reduction cover (gasket # 21395-KS4-690) after draining
the oil. There are three bearings in the final reduction cover --the previously
mentioned drive shaft bearing, a 23 mm countershaft needle bearing, and a 55 mm
final shaft bearing. Rotate the drive shaft within its bearing. Spin the needle
bearing and final shaft bearing with your finger. Spin the rear wheel and listen
for bearing noise. Remove the counter shaft gear, then the final gear while
spinning the rear wheel each time.
The only bearings now left in the crankcase are the drive shaft bearing,
countershaft needle bearing and final shaft bearing. The transmission
are easily examined for excessive wear and are removable. The first two bearings
can be checked by turning them with your finger. They should spin easily. Check
the countershaft bearing by spinning it with the countershaft. If good, remove
countershaft and gear. Spin rear wheel to see if noise still exists. Remove
final shaft gear and spin rear wheel again. Any bearing noise will have to be
the final shaft bearing or the swing arm bearing.
Next, as previously described, remove the swing arm assembly and check the 47 mm
bearing with your finger. This bearing is inexpensive along with the seals, so I
recommend replacing it. Spin the rear wheel to check the final shaft bearing.
This procedure has methodically isolated all the bearings in the drive train to
help you find the faulty one.
As a rule of thumb, if your scooter has 10K miles, I recommend opening up the
final reduction to examine the condition of the bearings and gears. I recommend
replacing the drive shaft bearing, the final shaft bearing and the swing arm
bearing to avoid future problems. If you replace one, do all of them. The cost
Once replaced, new bearings will give your ride years of comfortable and smooth
Randy Pozzi (Rev. 08/2006)