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Harley Davidson Intake Leak Symptoms

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There are a couple of general issues you’ve got to be prepared to face when dealing with engines. From mechanical to electrical, natural and even human causes, machine problems suck. Harley Davidson intake leaks are one of those issues you have to expect when using one.

How do you diagnose Harley Davidson intake leaks? What are the symptoms you should look out for? How do you fix them before they get out of hand? These and many other pieces of information you’ll come to learn in this short post.

What is a Harley Davidson intake leak?

An intake leak usually occurs when there is a fissure in a portion of the intake tract beyond your fuel delivery system. The leak can occur anywhere between the cylinder head and the carburetor slide. When this happens, some unmetered air finds its way into the motor engine. 

How do I diagnose Harley Davidson intake leaks?

This is a no-brainer. You’ve got a few tricks to play around with. Tug the clutch in and close the throttle. Naturally, if there’s an intake leak, the engine revs drop immediately.

Check for the leak itself, ignite and start up your motorcycle and allow it to idle. Get a propane torch and a bottle of probing spray oil (a water-filled squirt bottle will also help here). Turn on the propane torch but don’t light it. Apply the liquid in areas, and a change in RPMs is a sign you have a leak issue in your hand.

What are the Symptoms of Harley Davidson Intake Leak?

Harley Davidson Intake Leak Symptoms
Power Loss
Hesitation to Lean Issues
Engine Overheating
Low Oil Pressure
Bad Oil Viscosity
Air Intake Leaks Manifest in Several Ways

From power loss to hesitation to lean issues, engine overheating, low oil pressure, or bad oil viscosity, air intake leaks manifest in several noticeable and not-too-noticeable ways.

Usually, when there’s an intake leak, there’s a disproportionate ratio in the amount of air and fuel that flows into the engine. As a result, too, the additional oxygen mix increases engine temperatures, affects (reduces or increases) engine performance, and causes the air-fuel mixture to go leaner. Worst case, you’ve got to deal with readability issues, as well.

High idling is one issue that readily comes to mind. The first suspect is the air leak if you observe that your bike suddenly starts idling higher for no particular reason.

Also, there are hanging revs. This is a common and easily noticeable symptom like high idling. Hanging revs occur when the engine drops immediately after you pull the clutch in and close the throttle abruptly. When you notice this, there’s a big issue of an air leak threat. 

How do you fix a Harley Davidson intake leak?

Here’s a piece of headline-making news: diagnosing is the most difficult part of your job when you observe the Harley Davidson intake leak. Fixing is both simple and cheap. If you choose to opt for a DIY model, it is fine, but, why not try to engage the service of a professional? In that way, you wouldn’t have to repair and replace, over and over again.

To fix fissured intake boot symptoms, get a good seal before you start up your engine, and guess what, your motorbike engine is back to full capacity. Blowing the piston top may be damaging to the vacuum hoses because the latter are not often made of hard materials.

There’s also a chance that your V-twin intake isn’t properly aligned with the cylinder head. The best fix is to completely seal off the crack by reinstalling it. One or two steps, loosen the head, let the intake settle to a flush position, and then tighten it.

Also, if your carburetor needs a tight seal, go for Carburetor o-rings; they are both cheap and effective on your motorbike. It is better than merely loosening the throttle shaft or applying the felt spacers on the setups.


The truth is that the earlier you diagnose an intake leak, the better and easier the fix. Here’s a piece of rare advice you may not get elsewhere: ‘do not use aftermarket air parts to fix Harley Davidson intake leaks. Go for the OEM air parts.’ If you’re in doubt, then try to contact Harley Davidson customer service support. It is that important so that you fix your intake leak once and for all. Enjoy the full performance of your Harley Davidson bike, and bye for now! 

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Harley Davidson Intake Leak Symptoms

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