Rear Axle CV Boot Maintenance on the 1994 Yamaha YFM350ER MOTO-4
Shop parts for a 1994 Yamaha YFM350ER MOTO-4 ATV.
Root Causes of Boot Failure
CV boots on the 1994 Yamaha YFM350ER MOTO-4 take more stress per operating hour than most owners account for. Every hour of work use—hauling a loaded dump cart, running a plow, or navigating deep field ruts—flexes the rear axle boot through its fold range repeatedly under load. The boot is clamped at both ends of the CV joint and must flex continuously while maintaining a watertight seal against the specialized CV grease inside. Rubber that ages past its service window loses this ability gradually, hardening at the fold lines first, and eventually cracking under the flex loads it previously handled without issue.
On the YFM350ER MOTO-4, physical damage from rocks and debris is as common as age-related failure. The inner boot at the differential end of the rear axle is positioned close to the ground and exposed to anything displaced during field or off-road work. A single sharp rock can puncture a boot that was otherwise in serviceable condition, and the resulting grease loss starts with the first flex cycle after the puncture. Either failure mode puts the CV joint behind the boot on a wear timeline that accelerates with every subsequent ride.
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.
Recognizing CV Boot Problems Before Joint Damage
A failed CV boot on the 1994 Yamaha YFM350ER MOTO-4 typically shows itself through grease deposits near the rear axle before producing any noise. The spinning axle distributes CV grease onto the inner wheel, the rotor face, the brake assembly, or the adjacent frame when a boot tears. This pattern is distinctive—CV grease is thick, tacky, and dark—and builds up with each ride. Any time it appears near the rear axle of the YFM350ER MOTO-4, schedule an inspection before the machine goes back to work.
Remove the wheel and examine each boot by hand while rotating the axle. Look and feel for splits, cracks, clamp gaps, and grease on the boot exterior. The fold areas and the zones just inside both clamp bands are where damage appears first. A boot that looks intact but feels stiff or cracked at the folds should be replaced before it opens fully. A clicking or knocking from the rear axle during power turns or under acceleration is a sign that joint wear has already begun and the boot has been compromised long enough to allow contamination inside.
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.
Getting Organized for the Job
A rear CV boot replacement on the 1994 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.
Disassembly Steps
Raise the 1994 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.
What to Look for in the Joint
With the boot off the 1994 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.
Installing the Replacement Boot
Clean the CV joint completely on the 1994 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.
Completing the Service
Push the inboard axle end into the differential on the 1994 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 1994 Yamaha YFM350ER MOTO-4 ATV.
Shop Axles for a 1994 Yamaha YFM350ER MOTO-4 ATV.
Shop Lubricants & Solvents for a 1994 Yamaha YFM350ER MOTO-4 ATV.
Shop Wheel Bearings for a 1994 Yamaha YFM350ER MOTO-4 ATV.
Shop Skid Plates for a 1994 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.
