Tech Tips by Randy Pozzi

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#1 Breather Separator
#2 Drive Belt & Pulley Weight Rollers
#3 Startability & Driveability Problems
#4 CH250 Performance Upgrades
#5 CH250 Valve Adjustment
#6 Decals
#7 Pilot Screw Adjustment & Fix
#8 CH250 Driven Pulley/Clutch Repair
#9 Final Drive Oil Change
#10 Storing Your CH250 in Winter
#11 Hondaline Kenwood AM/FM Stereo
#12 Front Bumper Protector & Lower Cover Repair
#13 How To Buy A Good 1985-88 CH250
#14 Tires For The Honda CH 250
#15 CH250 Keihin Carb Float Valve Repair
#16 The Honda CH250: An Overview
#17 Honda CH250 Color Crossovers
#18 Honda CH250 Clock
#19 Keihin CV Carburetor Tuning
#20 Honda CH250 Oil Change
#21 Backfiring On Deceleration
#22 Parts Bin--What To Hoard For Your CH250
#23 Honda CH250 Maintenance
#24 So Your Honda Scooter Won't Start?
#25 How To Buy A Battery For Your CH250
#26 Honda CB350 Shocks To The Honda CH250
#27 1985-88 Honda CH250 Speedo Maintenance
#28 Honda CH-250 Antifreeze/Coolant Service
#29 CH250 Charging System Checks
#30  Final Reduction and Wheel Bearing Maintenance

#30  Final Reduction and Wheel Bearing Maintenance
Hello Group,

You 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 dry 
or start to rust, they will heat up, wear out of round and develop excess 
clearance.

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 reduction.

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 reduction 
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 races) 
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 gears 
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 is negligible.

Once replaced, new bearings will give your ride years of comfortable and smooth performance.

Randy Pozzi  (Rev. 08/2006)


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