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Motorcycle Exhaust Leak at Header – How To Diagnose & Fix

Exhaust leaks are not that uncommon on motorcycles. They’re harmless in most cases and easily detected just by the increase in engine noise by most experienced riders.

Luckily, exhaust systems in motorcycles are quite short when compared to those found in cars, and there are not a lot of places for exhaust leaks to occur other than right at the area where the headers and the cylinder head meet. The good news about that is that they’re very easy to fix and doing so shouldn’t cost you more than $50.

Exhaust Leak at Header Symptoms

While most riders will instantly notice that their motorcycle has an exhaust leak at the header, here are a handful of symptoms to help you rule out other unrelated problems if you’re unsure.

Distinct Ticking Noise

If you are riding and your motorcycle suddenly starts producing a new and noticeable ticking sound coming from the engine, that could be a sign of a leaking exhaust. Now, this can easily be confused with valvetrain noise (worn lifters, cam lobes, low oil pressure) so don’t rely on it 100%, however, this is by far the most common and noticeable symptom.

It normally happens with old exhaust headers, especially if they have been removed recently and the old exhaust gaskets were reused. The header collar nuts that attach to the cylinder head may also loosen with time and hence a small air gap can lead to a ticking sound.

Popping/Backfiring on Deceleration

Popping or backfiring on deceleration usually happens when the air-to-fuel mixture is lean or when there’s an exhaust leak at the header. A leak at the header area allows for cold air from the outside to momentarily enter the exhaust and mix with small bits of partially burnt fuel and detonate, thus producing a popping sound.

The unusual popping sound is not a foolproof indication of an exhaust leak since it can signify other problems. However, if the popping sound reduces slowly as the engine continues to run, then an exhaust leak is the more likely explanation since thermal expansion could reduce or close the leak.

Soot/Carbon Deposits Around the Leak Area

After some time, you may spot some soot or carbon deposits around the leak area. This is a definitive sign of an exhaust leak, but unfortunately – it takes quite some time for soot to accumulate around the leak.

Can an Exhaust Leak at the Header Damage the Engine?

Yes, although it’s very unlikely to happen! If the leak is big enough and you keep ignoring it, then the leak can cause damage to the engine. This is extremely rare though.

If the leak is bad enough, it can throw off the air-to-fuel mixture and make the engine run lean. An engine that’s running lean gets very hot and could eventually burn the exhaust valves, melt pistons, etc. Again, this is very rare but it can and does happen.

How to Check for Exhaust Leaks

Checking for motorcycle exhaust leaks is an easy process and will depend on the method that you choose. Here is a quick overview of the two different ways to go about it, but if you’re looking for a more in-depth how-to, check out our easy guide on checking for motorcycle exhaust leaks.

Using a Rag or a Paper Towel

This method is by far the easiest. The only things you’ll need are a rag and soapy water – that’s it. Make sure to do it while the engine is cold.

  • On a cold engine, cover the exhaust using a rag or a paper towel. Don’t worry, it won’t damage your engine.
  • Start the engine and quickly spray some soapy water on the exhaust, especially the area where the header connects to the cylinder head. You only have a few minutes to check for the leaks before the engine gets hot so act quick.
  • Check for bubbles. After spraying some soapy water, if you see some bubbles, then that shows the point where there is a leak.

Using a Vacuum Blower/Cleaner

A vacuum blower/cleaner like the Shop-Vac is the go-to for most people. Similar to the rag method above, it’s best to do it on a cold engine.

  • Fit the vacuum blower hose into your motorcycle exhaust. Ensure that the fitting is airtight and the motorcycle engine is cold to prevent the soapy water from evaporating too fast before you can locate the leak.
  • Turn on the vacuum cleaner/blower to create some pressure inside of the exhaust and sprinkle some soapy on the exhaust header collar or any other part of the exhaust pipe where you are suspecting the leak. As mentioned earlier, the leaks are mostly on the header where it connects to the engine cylinder.
  • Check for bubbles.

How To Fix Exhaust Leaks at the Header

There are only three ways for an exhaust leak to occur at the header: worn-out exhaust gaskets, loose header collar nuts, or corrosion of the headers themselves.

Worn-Out Exhaust Gaskets

If it’s the exhaust gaskets that are causing the leak, then fixing them is extremely easy.

  • Remove the exhaust headers from the cylinder head by undoing two bolts for each pipe
  • Move the exhaust headers enough to get to the old gaskets and remove them with a pick
  • Clean the mating surfaces with a wire brush
  • Carefully install the new header gaskets
  • Install the exhaust headers back to the cylinder head

Loose Header Collar Nuts/Bolts

If the leak is caused by loose nuts or bolts on the header collar, then consider yourself lucky. All you have to do is tighten them back to factory specifications with a torque wrench or by hand if it’s not your first rodeo.

However, if the leak is due to your exhaust header being rusty and corroded then you’re better off buying a new one or taking it to a professional at an exhaust shop if it’s salvageable.

Conclusion

Exhaust leaks are quite common and most of the time, they occur right where the exhaust headers meet with the cylinder head. Most riders can notice an exhaust leak immediately just by the change in sound coming from the engine.

Checking for exhaust leaks at the header is very simple. Luckily, exhaust leaks are unlikely to cause any damage to your engine.

In most cases, all you have to do is just retighten the nuts holding the exhaust headers to the cylinder head, as the fasteners get loose over time due to temperature cycles. But in some cases, the small manifold gaskets get worn out and no longer seal properly, thus causing an exhaust leak at the header.

Whichever the case, it’s best to get exhaust leaks fixed as soon as possible to avoid damage to the engine – especially when the leak is located at the header.

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