How to Replace Bearings in an RC Nitro Engine

Replacing the bearings in an RC nitro engine is an important maintenance job that can restore smooth operation, reduce vibration, and help extend the life of the engine.

At FastEddy Bearings, we supply replacement bearing kits for many popular RC nitro engines. One important thing to understand before installation is that our nitro engine bearings are shipped with rubber seals installed for protection during shipping, storage, and handling.

Depending on where the bearing is used in the engine, one or both rubber seals may need to be removed before installation.

The safest rule is simple:

Always configure the new FastEddy bearing to match the bearing you are removing from the engine.

Why Nitro Engine Bearings Are Different

Nitro engine bearings operate in a very demanding environment.

They are exposed to:

• High RPM
• Heat
• Fuel and oil
• Combustion residue
• Vibration
• Heavy internal loads

Unlike many wheel or drivetrain bearings, some nitro engine bearings rely on the engine's fuel-and-oil mixture for lubrication.

Because of this, a bearing that was designed to run open should not be replaced with a fully sealed bearing unless the original engine configuration calls for it.

FastEddy Bearings Are Shipped With Rubber Seals

FastEddy Bearings nitro engine bearings are typically supplied with rubber seals installed on both sides.

This helps keep the bearing clean and protected before installation.

However, those seals may not be the correct configuration once the bearing is installed in the engine.

Before installing the new bearing:

1. Remove the original bearing from the engine.
2. Inspect both sides carefully.
3. Note which side is sealed and which side is open.
4. Compare it directly with the new FastEddy bearing.
5. Remove the appropriate seal or seals from the new bearing so it matches the original.

The Rear or Inner Engine Bearing

The larger rear crankshaft bearing is located deeper inside the crankcase.

In many nitro engines, the rear bearing is open so the fuel-and-oil mixture inside the engine can lubricate it directly.

If the bearing you remove is open on both sides:

• Remove both rubber seals from the new FastEddy bearing.

Do not leave the bearing fully sealed if the original bearing was open.

The Front or Outer Engine Bearing

The smaller front bearing often uses a different seal arrangement.

In many engines:

• The outside seal remains installed.
• The inside seal is removed.

This allows lubrication from inside the engine to reach the bearing while the outer seal helps reduce contamination and leakage.

However, engine designs vary.

Do not assume every front bearing uses the same seal arrangement. Match the configuration of the bearing you remove.

Take Photos Before Disassembly

Before removing the original bearings, take clear photos showing:

• Which side of each bearing is sealed
• Which side is open
• Bearing orientation
• Crankshaft position
• Shims or spacers

These photos can make reassembly much easier.

Remove the Engine From the Vehicle

It is usually much easier to replace nitro engine bearings with the engine removed from the RC vehicle.

Depending on the model, you may need to remove or disconnect:

• Fuel lines
• Throttle linkage
• Exhaust system
• Clutch components
• Engine mounting screws

Clean the outside of the engine before opening it so dirt does not fall into the crankcase.

Disassemble the Engine Carefully

The exact process varies by engine, but replacing the bearings normally requires access to the crankshaft.

You may need to remove:

• Backplate
• Carburetor
• Cylinder sleeve
• Piston and connecting rod
• Crankshaft

Take your time and avoid forcing any internal engine parts.

Heat the Crankcase for Bearing Removal

Nitro engine bearings are usually installed tightly in an aluminum crankcase.

Heating the crankcase can make removal much easier because aluminum expands more than the steel bearing.

You can use:

• Heat gun
• Controlled oven
• Other appropriate controlled heat source

Never use an open flame.

Remove the Old Bearings

Depending on the engine design, useful tools may include:

• Bearing driver
• Brass drift
• Properly sized socket
• Wooden dowel
• Blind bearing puller
• Specialty nitro engine bearing removal tool

Apply force evenly and avoid damaging the aluminum bearing pocket.

Clean the Bearing Pockets

Once the old bearings are removed, clean the bearing pockets thoroughly.

Remove:

• Old oil
• Fuel residue
• Dirt
• Corrosion
• Metal particles
• Bearing debris

The new bearings should seat against a clean surface.

Prepare the New FastEddy Bearings

Before installation, place the old bearing next to the new FastEddy bearing.

Compare them carefully.

If the old bearing is open on both sides:

• Remove both rubber seals from the new bearing.

If the old bearing has one seal:

• Remove the appropriate seal from the new bearing.
• Leave the other seal installed.
• Install it in the same orientation as the original.

The bearing you remove is your guide.

How to Remove a Rubber Seal

Use a small:

• Pick
• Hobby knife
• Precision screwdriver
• Seal-removal tool

Carefully work the tip under the inner edge of the rubber seal and lift gently.

Avoid damaging the:

• Inner race
• Bearing cage
• Balls
• Seal that is being retained on the opposite side

Freeze the New Bearings

Placing the prepared bearings in a clean sealed bag and freezing them for approximately one hour can make installation easier.

Cooling causes the steel bearing to contract slightly.

Warm the Crankcase Before Installation

While the bearings are cooling, warm the aluminum crankcase evenly.

The combination of:

• Cold bearing
• Warm aluminum crankcase

can significantly reduce the force required for installation.

Install the New Bearings

Make sure each bearing is perfectly square before pressing it into the crankcase.

When pressing a bearing into a housing:

Apply pressure only to the outer race.

Do not press on the inner race when installing the bearing into the case. Doing so transfers installation force through the balls and can damage the bearing.

Double-Check the Seal Orientation

Before the bearings are fully installed, check them one more time.

Ask yourself:

Does each new bearing match the open and sealed sides of the bearing I removed?

If one seal is being retained, make sure it faces the same direction as the original bearing.

Allow the Engine to Cool

After installation, allow the engine case to return naturally to room temperature.

As the aluminum cools, it contracts around the bearings and secures them in place.

Reinstall the Crankshaft

Lightly lubricate the crankshaft and bearing surfaces with the appropriate engine lubricant.

Carefully reinstall the crankshaft and confirm that it rotates smoothly.

If you notice:

• Binding
• Grinding
• Excessive resistance
• Unusual play

Stop and inspect the installation before continuing.

Reassemble the Engine

Reinstall the remaining components according to the engine manufacturer's instructions.

Pay attention to:

• Connecting rod orientation
• Piston orientation
• Cylinder sleeve alignment
• Crankshaft shims
• Spacers
• Backplate orientation

Lubricate internal engine components appropriately during reassembly.

Common Nitro Engine Bearing Replacement Mistakes

• Installing new bearings with all rubber seals automatically left in place
• Removing seals without checking the original bearing first
• Removing the wrong seal from the front bearing
• Installing a one-seal bearing backward
• Blocking lubrication to a bearing that was designed to run open
• Hammering bearings into the crankcase
• Pressing on the inner race during installation
• Using excessive heat
• Using an open flame
• Forgetting crankshaft shims or spacers
• Reassembling internal engine parts without lubrication

Why Correct Seal Configuration Matters

A rubber seal is not automatically better in every bearing location.

In wheel hubs and many drivetrain applications, seals help protect the bearing from outside contamination.

Inside a nitro engine, certain bearings are designed to receive lubrication from the engine's fuel-and-oil mixture.

If a bearing that was originally open is replaced with a fully sealed bearing, lubrication may be restricted.

This can lead to:

• Excess heat
• Premature bearing wear
• Rough operation
• Bearing failure
• Engine damage

That is why the correct rule is:

Remove only the seals necessary to make the new FastEddy Bearings replacement match the bearing being removed and its location in the engine.

Signs Your Nitro Engine Bearings Need Replacement

Common symptoms include:

• Rough crankshaft rotation
• Grinding or growling noise
• Excessive crankshaft play
• Visible rust
• Metal debris inside the engine
• Increased vibration
• Unusual engine noise
• Bearing roughness during disassembly

Replacing worn bearings before they fail completely can help protect the crankshaft, connecting rod, piston, and engine case.

Should You Replace Both Engine Bearings?

If the engine is already being disassembled because one crankshaft bearing is worn or damaged, it is often a good idea to inspect both bearings carefully and consider replacing them together.

Both bearings have usually experienced similar:

• Run time
• Heat cycles
• Fuel exposure
• Lubrication
• Moisture
• Storage conditions

Replacing both during the same rebuild may prevent having to completely disassemble the engine again soon afterward.

Why Choose FastEddy Bearings?

FastEddy Bearings offers replacement bearing kits for many popular RC nitro engines.

Our nitro engine bearing kits provide:

• Model-specific bearing selection
• Correct bearing sizes for the listed engine
• Quality rubber sealed bearings
• Protection during shipping and storage
• Removable seals for proper engine configuration
• No searching for individual bearing sizes
• No guesswork
• Fast order processing and shipping

Most importantly, remember that the rubber seals installed when you receive the bearings may need to be removed before installation.

Frequently Asked Questions

Why does my FastEddy nitro engine bearing have rubber seals when my original bearing is open?

FastEddy Bearings ships the replacement bearing with rubber seals to protect it during storage, shipping, and handling. Remove the necessary seal or seals before installation so the replacement matches the original bearing.

Should I remove both rubber seals?

Only if the bearing you are replacing is open on both sides. Do not automatically remove both seals from every engine bearing.

What about the front engine bearing?

Many nitro engines use a front bearing that is open toward the inside of the engine while retaining a seal toward the outside. If that matches your original bearing, remove the inside seal and retain the outside seal.

What about the rear engine bearing?

Many rear crankshaft bearings are open so the engine's fuel-and-oil mixture can lubricate them. If your original rear bearing is open on both sides, remove both seals from the replacement.

How do I know which seals to remove?

Look at the bearing you are removing and configure the FastEddy replacement to match it. Also consult the engine manufacturer's instructions when available.

Can I leave both seals installed if the bearing fits?

Only if that matches the original engine bearing configuration. A seal in the wrong location can interfere with proper lubrication.

Final Thoughts

Replacing bearings in an RC nitro engine requires more care than replacing wheel or drivetrain bearings, but it is a manageable maintenance job for an experienced RC hobbyist.

Cleanliness, controlled heat, proper tools, correct installation pressure, and careful reassembly are all important.

But the most important point is this:

FastEddy Bearings ships nitro engine bearings with rubber seals installed for protection. Before installation, inspect the bearing being removed and remove the appropriate seal or seals from the new bearing so it matches the original bearing's configuration and location in the engine.

Match what you remove. Install the replacement in the same orientation.

Taking the time to do this correctly helps ensure the bearing receives the lubrication intended by the engine manufacturer and gives your rebuilt nitro engine the best opportunity for smooth, reliable operation.