How to Replace Briggs and Stratton Camshaft

Table of Contents

Replacing a Briggs and Stratton camshaft can seem daunting, but it’s a manageable DIY project with the right tools and guidance. This comprehensive guide walks you through diagnosing camshaft issues, gathering necessary components, and performing a step-by-step replacement, from engine disassembly to reassembly and testing. Understanding engine timing marks and careful handling are crucial for a successful repair. By following these instructions, you can restore your small engine’s power and performance efficiently.

How to Replace Briggs and Stratton Camshaft

There’s nothing quite like the satisfaction of a well-running small engine, whether it’s powering your lawnmower, pressure washer, or generator. But what happens when that reliable Briggs and Stratton engine starts sputtering, backfiring, or refuses to start altogether? Often, the culprit might be something deep inside its mechanical heart: the camshaft. If you’ve been putting off this repair because it seems too complex, don’t worry! This comprehensive guide will walk you through how to replace a Briggs and Stratton camshaft, step by step, empowering you to bring your engine back to life.

Replacing a Briggs and Stratton camshaft might sound like a job for a professional mechanic, but with a bit of patience, the right tools, and clear instructions, it’s a perfectly achievable DIY task for many home mechanics. We’ll break down the process into easy-to-follow sections, covering everything from diagnosing the problem to getting your engine fired up again. By the end of this article, you’ll have the confidence to tackle this repair and enjoy the fruits of your labor: a smooth-running engine and the satisfaction of a job well done.

Key Takeaways

Diagnosis is Key: Before attempting to replace your Briggs and Stratton camshaft, accurately diagnose the problem. Common symptoms include a “no start” condition, backfiring, loss of power, or unusual ticking/knocking noises, often stemming from worn lobes or a faulty compression release mechanism.
Safety and Preparation First: Always disconnect the spark plug wire and drain all fluids (oil, fuel) before starting any engine work. Work in a well-ventilated area and gather all your tools and the new camshaft part in advance to ensure a smooth workflow.
Understanding Engine Timing: The most critical step during camshaft replacement is aligning the timing marks on the camshaft and crankshaft gears correctly. Incorrect timing will prevent the engine from starting or cause severe damage.
Careful Disassembly and Reassembly: Take photos or notes during disassembly, especially when dealing with multiple fasteners or tricky components. This helps immensely during reassembly, ensuring every part goes back in its correct place and is torqued appropriately.
Inspect Related Components: While the engine is open, take the opportunity to inspect other accessible components like the crankcase gasket, crankshaft, pushrods, and valve springs for wear or damage. Replace any worn parts to prevent future issues.
Fresh Fluids and Proper Break-in: Always refill with fresh, clean oil and fuel after the replacement. Consider a short break-in period or gentle initial operation to allow new parts to settle, and check for any leaks or unusual sounds immediately after starting.

Quick Answers to Common Questions

What are the common signs of a bad Briggs and Stratton camshaft?

Common signs include difficulty starting, no start condition, backfiring, loss of power, surging, or unusual ticking/knocking noises coming from the engine.

Do I need special tools to replace a Briggs and Stratton camshaft?

While most standard mechanic’s tools (sockets, wrenches, screwdrivers) are sufficient, a torque wrench is essential for properly tightening bolts to manufacturer specifications, ensuring a good seal and preventing damage.

Is it necessary to replace the crankcase cover gasket when replacing the camshaft?

Yes, absolutely. You must always replace the crankcase cover gasket with a new one to ensure a proper, leak-free seal after removing and reinstalling the cover.

How do I make sure I install the new camshaft correctly regarding timing?

The most critical step is to align the timing marks (usually small dots or lines) on both the camshaft gear and the crankshaft gear perfectly when you slide the new camshaft into place. This ensures correct valve timing.

What should I do if my engine doesn’t start after replacing the camshaft?

First, recheck the spark plug connection and ensure there’s fuel. The most common cause for a no-start after camshaft replacement is incorrect timing. You may need to re-open the engine and verify the timing marks are perfectly aligned.

📑 Table of Contents

1. Understanding the Briggs and Stratton Camshaft: Why It Fails
2. Gathering Your Tools and Supplies: Preparation is Key
3. Pre-Disassembly: Getting Ready for Surgery
4. Disassembly: Accessing the Camshaft
5. Camshaft Replacement and Reassembly: The Critical Steps
6. Post-Replacement Checks and First Start
Conclusion

1. Understanding the Briggs and Stratton Camshaft: Why It Fails

Before we dive into the nitty-gritty of replacement, let’s briefly touch upon what a camshaft does and why it might need replacing. The camshaft is like the conductor of an orchestra for your engine’s valves. It has lobes (oval-shaped protrusions) that, as the shaft rotates, push against followers or lifters, which in turn open and close the intake and exhaust valves at precisely the right moments. Many Briggs and Stratton engines also incorporate an automatic compression release (ACR) mechanism on the camshaft, designed to make starting easier by slightly opening an exhaust valve during the cranking cycle.

Symptoms of a Bad Camshaft

Identifying the symptoms early can save you a lot of headache. If your engine is experiencing any of the following, a failing Briggs and Stratton camshaft could be the issue:

Hard Starting or No Start: This is one of the most common signs, especially if the compression release mechanism is faulty. The engine might crank but won’t catch, or it might feel like it has too much compression to turn over.
Backfiring Through the Carburetor or Exhaust: Incorrect valve timing, often caused by a worn camshaft lobe, can lead to fuel igniting at the wrong time.
Loss of Power or Surging: If valves aren’t opening or closing fully or at the right time, combustion efficiency drops, leading to noticeable power loss or an engine that “hunts” or surges.
Unusual Ticking, Clicking, or Knocking Noises: Worn camshaft lobes, damaged lifters, or issues with the compression release can create abnormal mechanical noises from within the engine.
Bent Pushrods: Sometimes, a failing compression release can cause a valve to stay open too long, leading to a piston hitting a valve, which bends the pushrod. This is a severe symptom that almost certainly points to camshaft trouble.

Common Causes of Camshaft Failure

While Briggs and Stratton camshafts are built to last, they aren’t immortal. Here are some reasons they fail:

Wear and Tear: Over time, the constant friction between the camshaft lobes and the valve lifters/tappets can cause the lobes to wear down. This changes valve timing and lift.
Oil Starvation: Lack of proper lubrication is a camshaft’s worst enemy. Running the engine with low or dirty oil greatly accelerates wear.
Faulty Compression Release: The automatic compression release mechanism can fail, preventing the engine from effectively lowering compression during starting, making it very hard to pull-start or turn over with the electric starter.
Manufacturing Defects: Though rare, a defective camshaft can sometimes fail prematurely.
Impact Damage: External impacts or internal debris can sometimes damage the camshaft or its associated gears.

2. Gathering Your Tools and Supplies: Preparation is Key

Before you even think about cracking open your engine, you need to be prepared. Having all your tools and replacement parts ready will make the process much smoother and prevent frustrating interruptions.

Essential Tools You’ll Need

Socket Set and Wrenches: A good set of metric and/or SAE sockets and wrenches (depending on your engine model) will be indispensable.
Torque Wrench: Absolutely critical for correctly tightening crankcase cover bolts and other components to factory specifications.
Screwdrivers: Flathead and Phillips head.
Pliers: Needle-nose and regular.
Gasket Scraper or Razor Blade: For removing old gasket material.
Rubber Mallet: For gentle persuasion during disassembly or reassembly.
Feeler Gauges: For checking valve lash, if adjustable.
Magnetic Pickup Tool: Invaluable for retrieving dropped bolts or small parts.
Container for Parts: Bowls or labeled bags to keep fasteners organized.
Shop Rags and Cleaner: For keeping things tidy.
Drain Pan: For old oil and fuel.
Work Gloves and Safety Glasses: Essential for personal protection.

Replacement Parts

You’ll definitely need a new Briggs and Stratton camshaft. Make sure you get the correct part number for your specific engine model. You can usually find the model, type, and code numbers stamped on the engine itself.

New Camshaft: Ensure it’s the exact replacement for your engine.
Crankcase Cover Gasket: You *must* replace this. Never reuse an old gasket.
Engine Oil: Fresh oil, as specified by Briggs and Stratton for your engine.
Optional: New pushrods, valve lifters/tappets, oil seals, or a full gasket set if other components show wear.

3. Pre-Disassembly: Getting Ready for Surgery

Safety and cleanliness are paramount. Take your time with these initial steps.

Safety First!

Always disconnect the spark plug wire from the spark plug. This prevents accidental starting of the engine while you’re working on it, which could lead to severe injury.

Draining Fluids

First, drain all the engine oil into a suitable pan. Many Briggs and Stratton engines have a drain plug at the bottom or a dipstick tube that can be used for draining. Next, if applicable, drain the fuel tank. You can often siphon it out or disconnect the fuel line from the carburetor and let it drain into a safe container.

Cleaning the Engine

Before you start removing parts, give the exterior of the engine a good cleaning. Dirt and debris can easily fall into the engine’s internals once you open it up, causing potential problems. Use a brush and some engine degreaser, then rinse and let it dry.

4. Disassembly: Accessing the Camshaft

This is where the real work begins. Be methodical and organized.

Removing Ancillary Components

You’ll need to remove anything obstructing access to the crankcase cover. This typically includes:

Muffler: Unbolt and remove.
Fuel Tank: Disconnect fuel lines and unbolt.
Carburetor and Air Cleaner Assembly: Remove the air filter housing, then the carburetor itself.
Blower Housing and Flywheel (if necessary): On some models, the blower housing and even the flywheel might need to be removed to access all crankcase cover bolts or to rotate the engine easily.
Engine Mounts/Equipment: If the engine is mounted to a piece of equipment (like a lawnmower deck), you might need to unbolt it from the frame and move it to a workbench for better access.

Keep all bolts and parts organized, perhaps in labeled bags or containers, so you know exactly where they go during reassembly.

Removing the Crankcase Cover

The camshaft is housed within the crankcase, behind the crankcase cover (also sometimes called the side cover or sump).

Locate and Remove Bolts: Find all the bolts holding the crankcase cover to the engine block. There can be quite a few, and they might be of different lengths. Pay attention to which bolt came from where.
Gently Pry Off the Cover: Once all bolts are removed, the cover might be stuck due to the old gasket and sealant. Use a rubber mallet to gently tap around the edges of the cover. You can also carefully use a flathead screwdriver or gasket scraper in designated pry points (if available) to separate the cover. Do not force it or damage the mating surfaces.
Clean Mating Surfaces: Once the cover is off, carefully remove all traces of the old gasket material from both the engine block and the crankcase cover. A gasket scraper or razor blade works well, but be extremely careful not to gouge or scratch the aluminum surfaces. Any imperfections can lead to oil leaks.

With the crankcase open, you’ll see the camshaft, crankshaft, and possibly the oil slinger.

Remove the Old Camshaft: The Briggs and Stratton camshaft typically just slides out of the engine block once the crankcase cover is removed. You might need to gently wiggle it. Be careful not to drop the valve lifters/tappets, which will likely be loose now.
Inspect the Old Camshaft: Examine the lobes for excessive wear, pitting, or flat spots. Check the gear for missing or chipped teeth. Inspect the compression release mechanism for damage or improper function.
Inspect Lifters and Pushrods: Remove the valve lifters (sometimes called tappets) and inspect their contact surfaces for wear or cupping. Also, check the pushrods for any bends or damage. This is a good time to replace these if they show significant wear.

5. Camshaft Replacement and Reassembly: The Critical Steps

This is where precision is key, especially regarding engine timing.

Understanding Timing Marks

The most crucial step in installing a new Briggs and Stratton camshaft is correctly aligning the timing marks. Both the camshaft gear and the crankshaft gear will have a small dot, punch mark, or line. These marks must align perfectly when the gears mesh.

Locate Marks: Before installing the new camshaft, identify the timing mark on the crankshaft gear. You might need to rotate the crankshaft slightly to bring it into view.
Align and Install: Carefully slide the new camshaft into the engine block, ensuring the timing mark on its gear aligns perfectly with the timing mark on the crankshaft gear. The gears should mesh cleanly. This ensures your valves open and close at the correct intervals relative to the piston’s position.

Reinstalling the Crankcase Cover

Install New Gasket: Place a new crankcase cover gasket onto the engine block, making sure it aligns with all bolt holes and passages. You can use a thin layer of gasket sealant (permissible for some gaskets, check instructions) to help hold it in place and ensure a good seal, but often dry is fine.
Replace Valve Lifters and Pushrods: If you removed or replaced the valve lifters, carefully insert them back into their bores. Ensure they are seated correctly. Place the pushrods back into their respective lifters, guiding them towards the valve rocker arms (you might need to rotate the engine slightly to ensure the camshaft lobe isn’t pushing a lifter up too high yet).
Attach Cover: Carefully position the crankcase cover back onto the engine block, aligning it with the bolt holes. Gently push it into place.
Torque Bolts: Reinstall all the crankcase cover bolts. Start them all by hand to prevent cross-threading. Then, tighten them in a specific sequence (usually a star or criss-cross pattern) to the manufacturer’s specified torque using your torque wrench. This ensures even pressure on the gasket and prevents warping of the cover. Refer to your engine’s service manual for the exact torque specifications.

Reattaching Engine Components

Now, it’s time to put everything back together in reverse order of disassembly.

Reinstall Carburetor, Air Cleaner, Fuel Tank, and Muffler: Carefully reattach all components, ensuring all gaskets, seals, and fuel lines are correctly installed and tightened.
Connect Spark Plug Wire: Once all is securely back in place, reattach the spark plug wire.
Double-Check: Take a moment to visually inspect all connections, bolts, and hoses to ensure everything is tight and in its proper place.

6. Post-Replacement Checks and First Start

You’re almost there! A few final steps before you hear that sweet sound of a running engine.

Adding Fresh Fluids

Fill with Oil: Add the recommended type and amount of fresh engine oil to the crankcase. Check the dipstick to ensure it’s at the correct level.
Fill with Fuel: Fill the fuel tank with fresh gasoline.

Initial Start-Up Tips

Prime the System: If your engine has a primer bulb, give it a few presses.
Start Gently: Pull the starter rope or engage the electric starter. Don’t be alarmed if it takes a few more cranks than usual to start, as fuel lines and the carburetor may need to re-prime.
Listen and Observe: Once the engine starts, let it run for a few minutes. Listen for any unusual noises (knocking, ticking, excessive valve clatter). Check for any oil or fuel leaks around the crankcase cover and fuel lines.
Test Under Load: If everything sounds and looks good, you can test the engine under a light load to ensure it’s performing correctly. Your Briggs and Stratton camshaft replacement is complete!

Troubleshooting Common Issues

If your engine doesn’t start or runs poorly after replacement:

No Start: Double-check spark, fuel, and compression. Ensure the spark plug wire is connected. Recheck the timing marks – this is the most common error with camshaft replacement.
Backfiring: Almost always an indication of incorrect valve timing. You’ll need to reopen the crankcase cover and re-align the camshaft and crankshaft timing marks.
Oil Leak: Inspect the crankcase cover gasket. It might not be seated correctly, or the bolts might not be torqued evenly.
Bent Pushrods: If the engine turns over very hard or makes a loud metallic clang, stop immediately. You might have bent a pushrod, likely due to incorrect valve timing or lifter issues.

Conclusion

Congratulations! You’ve successfully learned how to replace a Briggs and Stratton camshaft. This repair might seem daunting at first, but by following these detailed steps, you’ve not only saved money but also gained valuable mechanical experience. Remember, patience, precision, and adherence to torque specifications are your best friends during this process. Now, enjoy the renewed power and smooth operation of your Briggs and Stratton engine, knowing you did the job right! Keep up with regular oil changes and maintenance, and your engine will serve you well for years to come.

Frequently Asked Questions

How long does it typically take to replace a Briggs and Stratton camshaft for a DIYer?

For someone with moderate mechanical experience, replacing a Briggs and Stratton camshaft can take anywhere from 3 to 6 hours, assuming all tools and parts are readily available. It might take longer for first-timers, especially with engine cleaning and careful disassembly/reassembly.

What is the function of the compression release mechanism on a Briggs and Stratton camshaft?

The automatic compression release (ACR) mechanism is a small device on the camshaft that slightly opens an exhaust valve during the engine’s cranking cycle. This reduces compression, making it much easier to pull-start the engine or for the electric starter to turn it over, especially on larger single-cylinder engines.

Can I reuse the old valve lifters and pushrods when replacing the camshaft?

While you theoretically can, it’s highly recommended to inspect them thoroughly. If the old valve lifters show any signs of pitting, wear, or cupping, or if the pushrods are bent, they should be replaced. New camshafts prefer to mate with new, unworn lifters for optimal performance and longevity.

Are there different types of Briggs and Stratton camshafts, and how do I ensure I get the right one?

Yes, Briggs and Stratton produces many different engine models, and camshafts are specific to these models. To ensure you get the correct replacement, always refer to your engine’s model, type, and code numbers (usually found stamped on the engine shroud or block) and cross-reference them with the official Briggs and Stratton parts list.

What is the importance of using a torque wrench during reassembly?

A torque wrench is crucial because it allows you to tighten bolts to the manufacturer’s exact specifications. Over-tightening can strip threads or warp components, while under-tightening can lead to leaks or parts coming loose, especially for critical components like the crankcase cover bolts.

What kind of maintenance can help prevent future camshaft failure?

The best prevention is consistent and proper engine maintenance. Regularly check and change your engine oil according to the manufacturer’s schedule, using the correct type and viscosity of oil. Keeping the engine clean and avoiding overheating also contribute significantly to the longevity of internal components like the camshaft.