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2-Stroke Exhaust Leak Repair Guide

By: Leon Rhodes

2-stroke exhaust systems are subjected to extreme heat and vibration during regular use which, over-time, can cause exhaust system corrosion and leaks. Exhaust leaks rob the engine of performance, are sometimes loud and can cause unsafe operating conditions.

Dirt Bike Exhaust

Replacing the exhaust system on a 2-stroke (or 4-stroke) ATV, dirt bike or side-by-side engine can be expensive, fortunately you may be able to save some money and repair an exhaust leak yourself. The goal of this article is to help you get a little more life out of your exhaust components without welding or spending much money.

1. Find the exhaust leak (the hard part)

Before you can fix an exhaust leak you have to figure out where it is. Leak locations are not always obvious until they get big enough that repair may not be possible.

In my experience, exhaust leaks typically happen on the bottom side of pipes and flanges(connections) where moisture collects and causes rust to form. This is especially common near the engine, however, leaks can happen anywhere.

With the engine running start by visually inspecting the exhaust side of the engine, the leak location may or may not be visible(usually not). Resist any urge to feel for air movement, the exhaust system gets really hot.

If the leak location is obvious, great, move onto step two. If it's not, and it isn't most of the time, here are some tips and tricks to help you find the exhaust leak.

Check for missing or damaged hardware. Visually inspect any connections for broken or missing bolts or clamps. The easiest fix is tightening or replacing missing hardware so check for that first. The hardest is replacing broken bolts, but check for those too.

Perform a sound test. Sometimes it's possible to hear where an exhaust leak is located even if you can't see it. Listen for a pulsing, hissing or ticking sound similar to the noise an exhaust makes but sharper and coming from closer to the engine. It helps if you move/turn your head as you listen so that you can get a better idea on the direction the sound is coming from.

Squeeze connecting flanges together. If possible, and while wearing heat-resistant gloves for safety, use a pair of pliers or vice grips to gently squeeze connecting flanges together. If the leak is coming from between the flanges the sound of the leak may change or disappear.

If the sound increases it typically means the leak is on the outside of the connectors, or on the other end of the flange. Repeat the process in different locations on the flange if you can safely reach them.

Pressurized exhaust leak test. A pressure test, sometimes called a smoke test, can help you find the exhaust leak. Let the exhaust system cool down and pressurize it from the muffler end so that you can perform a leak test. You can do this using common shop tools such as a leaf blower or air compressor and some duct tape to secure it to the muffler.

Next, using a bottle of soapy water, spray the area where you suspect the exhaust leak is located. If there is a leak the soapy water solution will create bubbles over it.

2. Determine if removal is necessary (important)

Some exhaust leaks can be patched or sealed without removing the exhaust system. Removal sometimes makes it easier to properly repair a leak but it always risks creating another problem, namely a dreaded broken bolt. From years of experience and having repaired dozens of broken flange and manifold bolts I can tell you that, sometimes, it's better to repair the exhaust system without removing it.

Once you know where the leak is you can better determine if removal is necessary. Exhaust leaks between connections typically mean a gasket or o-ring seal has failed and will require removal to replace. Check to see if the bolts and/or springs are tight around the connection to make sure. For other types of exhaust leaks you have other repair options.

3. When to use putty to fix an exhaust leak

Extreme heat putty specifically designed for exhaust systems is best used to repair small exhaust leaks near welds or connections. With the engine cold the putty is applied by hand and allowed to cure until it hardens into a steel-like compound.

Follow the manufacturer's instructions carefully if you decide to go with putty and make sure the area is clean before application. A wire brush is useful for removing any rust flakes that could ruin a putty repair. Exhaust putty is available at most auto-parts stores.

Repair Tip: Don't start the engine after applying putty until the putty has fully cured. Doing so will cause exhaust pressure to push the putty out of the opening before it can fully harden.

4. When to use band clamps to fix an exhaust leak

An exhaust band clamp is a wide piece of metal, typically stainless steel, that wraps around an exhaust leak and is tightened with bolts to create a tight seal. Band clamps should be used to seal medium to large holes or cracks in straight sections of the exhaust system.

Band clamps are not designed to work in curved locations and do not work to seal leaks next to flanges or other connections. The band clamp must be able to cover the entire leak with extra space on BOTH sides.

Repair Tip: When fixing a cracked exhaust with a band clamp, a thin bead of exhaust putty can first be applied to the crack to help prevent it from getting longer.

5. When to use muffler tape to fix an exhaust leak

Muffler tape is an extremely sticky(on both sides) bandage-like roll of material that hardens when exposed to heat and air. It's best to use muffler tape to seal exhaust leaks in pipe bends where a straight clamp wouldn't work.

Muffler tape is a less permanent repair solution when compared to a clamp, which typically outlasts the exhaust system. For best results limit tape use to bends or other areas a band clamp won't work. As always, follow the manufacturer's instructions carefully.

6. Safety precautions and maintenance

Wear proper gloves and eye protection whenever working on a small engine because they can get extremely hot and cause burns.

If your 2-stroke or 4-stroke exhaust system is of newer design and has easily removable sections consider replacing the o-rings as part of your regular maintenance schedule. The best leaks are the ones that never happen!

- Frequently Asked Questions

What are 2-stroke exhaust leak symptoms?

An exhaust leak on your 2-stroke engine can cause rough idle, poor response and a tell-tale stain where unburned fuel mix might be leaking from the exhaust. Other symptoms include a louder than usual sounding exhaust and backfiring when the silencer gets hot.

What is the best way to fix a 2-stroke header leak?

Exhaust headers are typically made from cast iron or heavy gauge steel which responds well to repair welding. A welded exhaust leak in the manifold is typically a permanent fix. Exhaust putty is another option.

Are exhaust leaks easy to fix?

Exhaust leaks are easy to fix once you know where they are and which type of fix is required. The hardest part about fixing an exhaust leak yourself is finding it and choosing the right repair option.

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