1992 Yamaha YFM350ER MOTO-4 Rear CV Boot Service Guide
Shop parts for a 1992 Yamaha YFM350ER MOTO-4 ATV.
How the Rear CV Boot Wears Out
The rear CV boot on the 1992 Yamaha YFM350ER MOTO-4 seals the constant-velocity joint on the rear axle from the working conditions a utility ATV encounters. Mud, water, rocks, and sustained torque loads all contribute to boot wear at a rate that exceeds what recreation-only use would produce. The boot flexes at its fold lines with every inch of rear suspension travel, and the compound that makes up the boot must maintain its elasticity across years of this repetitive flexing. UV radiation from sunlight degrades the rubber even during periods the machine is stored between uses.
When the boot finally fails on the YFM350ER MOTO-4—through a UV-related crack at the fold lines or a physical puncture from debris—CV grease begins to exit through the opening with every rotation and trail contamination enters through the same path. The precision bearing surfaces inside the joint that were running on clean, sealed grease are now running on an increasingly contaminated supply, with the contamination level rising with each ride. Catching the failure before the joint sustains damage is the difference between a boot kit repair and a full axle replacement.
As a 2WD utility ATV, the YFM350ER MOTO-4 drives only the rear wheels. The CV boots are located on the rear axle only—the front wheels steer and roll freely without a driven axle, so this service is rear-focused.
How to Spot a Torn or Cracked Boot
Finding a failing CV boot on the 1992 Yamaha YFM350ER MOTO-4 before it damages the joint requires knowing the specific evidence. The most visible sign is grease on a surface adjacent to the rear axle—the inner wheel, the rotor, the brake caliper, or the lower frame. A rotating axle distributes CV grease widely once a boot tears, and the deposits accumulate over successive rides. CV grease is visually distinct from road grime and doesn’t blend in with mud or dust. Spotting it on the YFM350ER MOTO-4 near the rear axle warrants an immediate inspection.
Raise the YFM350ER MOTO-4 on jack stands and remove the rear wheel to access the boot. Grip each boot and rotate the axle, looking and feeling for tears, cracks, punctures, and clamp gaps. The fold lines are the most common cracking location, and the zones near both clamp bands are where physical damage tends to concentrate. A boot with visible surface cracking that hasn’t opened fully yet should be replaced in the same session. A clicking or popping sound from the rear end during load tells you the joint behind the boot has already seen some wear.
On the YFM350ER MOTO-4, CV boot service is rear-axle work. The front wheels are not driven and have no CV joints to service on this machine.
What to Have Ready
A rear CV boot replacement on the 1992 Yamaha YFM350ER MOTO-4 requires: a floor jack and two jack stands; an axle nut socket in the correct size for the YFM350ER MOTO-4; a torque wrench; snap-ring pliers for the differential-end retaining clip; boot clamp pliers or an ear-crimp tool; and shop rags. The CV boot kit must include the replacement boot, both clamp bands, and the correct CV grease. CV joints operate under high contact pressure between their precision bearing balls and races, and they require a molybdenum-based compound to maintain adequate film strength at those loads. Using a substitute grease type reduces protection and shortens joint service life.
Set a drain pan under the axle area before starting. Old contaminated grease from a torn boot needs to come out of the joint completely before new grease goes in. MotoSport.com stocks CV boot kits and axle assemblies for the YFM350ER MOTO-4.
Getting to the Torn Boot
Raise the 1992 Yamaha YFM350ER MOTO-4 on jack stands and remove the rear wheel on the affected side. Remove the cotter pin and axle nut. Push the axle spline inward to separate it from the hub—use a hub puller if the YFM350ER MOTO-4 has a tight spline fit. At the inboard end, compress the snap ring at the differential housing with snap-ring pliers and pull the axle free. Lay it on a clean surface, cut both clamp bands, and slide the damaged boot off the shaft. Clean the clamp groove areas on both the axle shaft and differential housing before installing the replacement boot on the YFM350ER MOTO-4.
CV Joint Condition Check
With the boot off the 1992 Yamaha YFM350ER MOTO-4, clean old grease from the CV joint and articulate it through its full designed range—compression and extension along the shaft plus full angular rotation. Smooth, even motion through the entire range indicates a serviceable joint. Roughness or grinding at any point in the articulation means bearing wear that repacking won’t fix. Hold the shaft and push the outer housing in non-articulating directions to check for play. Any clunking or excess movement outside the designed articulation range on the YFM350ER MOTO-4 means the axle needs replacement, not just a new boot.
Fresh Grease and Boot Installation
Clean the CV joint completely on the 1992 Yamaha YFM350ER MOTO-4—housing, bearing balls, and inner race free of all old grease and contamination. Slide the new boot onto the shaft before reconnecting the joint end. Pack the CV grease from the YFM350ER MOTO-4’s kit into the joint by hand, filling the bearing pockets and rotating the housing for even distribution. Use the full quantity. Seat the new boot with both ends in the clamp grooves, crimp both clamps fully, and verify neither rotates. MotoSport.com stocks CV boot kits for this ATV.
Putting It Back Together
Push the inboard axle end into the differential on the 1992 Yamaha YFM350ER MOTO-4 until the snap ring seats positively. A hand-pull should confirm it’s locked. Guide the outboard spline into the hub, install the axle nut, and torque to the YFM350ER MOTO-4’s specification. Secure with a new cotter pin or re-stake the nut as appropriate. Reinstall the wheel and torque the lug nuts. Lower the YFM350ER MOTO-4 and cycle the rear suspension through its range to check for boot clearance. A brief low-speed test confirms the repair is complete. MotoSport.com stocks CV boot kits and axle assemblies for this ATV.
Related Shopping Categories
Shop CV Joints for a 1992 Yamaha YFM350ER MOTO-4 ATV.
Shop Axles for a 1992 Yamaha YFM350ER MOTO-4 ATV.
Shop Lubricants & Solvents for a 1992 Yamaha YFM350ER MOTO-4 ATV.
Shop Wheel Bearings for a 1992 Yamaha YFM350ER MOTO-4 ATV.
Shop Skid Plates for a 1992 Yamaha YFM350ER MOTO-4 ATV.
Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your ATV's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.
