4 Major Harley Davidson 103 Engine Problems & Solutions

The Harley 103 engine develops some unfortunate issues over time. These issues pop up as the engine hits over a thousand miles on the odometer.  While some of these problems can only be resolved by a professional, others can be resolved by the owner with basic repair knowledge.

Also, by taking care of the problems before they become serious, you can prolong the life of your Harley 103 and prevent it from failing catastrophically. So let’s go in depth about the Harley 103 engine problem symptoms and their potential fixes.

4 Common Harley Davidson 103 Engine Problems

The conventional engineering with old designs and technology, the Harley 103 engine generates some issues which need tending before it becomes too late. Here are some common problems you might face with your 103 engine.

  • Primary Automatic Chain Tensioner
  • Pressed Flywheels Wearing Out
  • Periodic Misfiring
  • Excessive Engine Overheating

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Troubleshooting and Fix For Harley 103 Engine Problems

Now that we know what could possibly be wrong with the 103 engine, let’s take a peek at the diagnosis and possible fixes to avoid the issues.

Stock Chain Tensioner Issue

While shifting gears hard, it tends to ratchet up tighter, resulting in pulling everything closer to it, such as the crankshaft, and transmission. This is one reason the six-speed transmission system has too many troubles. 

Because once it goes up, it does not come down or compensate for tight or loose spots on the chain. Hence, it leads to early degeneration of the transmission system. 

In the long run, you would miss the smooth shifting experience and a lot of chain noise from the engine. 

To overcome this issue, you can go with the manual chain tensioner or a better yet compatible aftermarket primary chain tensioner such as Hayden.

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Pressed Flywheel/Crankshaft Wearing Out

This is one of the design flaws of the Harley twin cam 103 engine. In earlier models of the engine, the flywheels used to be held together by a crank bolt and nut torqued down to hold both sides of the flywheel. 

But in this particular model, the flywheel is pressed together by around 400-ton pressure at the factory. 

As a later with every mile being added to the odometer, it will come out sooner or later depending upon the riding conditions.

You might feel the difference that it has become out of true around 15000 miles or more. 

On the cam side, the silent chains start to wobble coming out of the truth. Since nothing is holding the flywheel assembly it starts to wear the bushes, bearings, and shafts resulting in major engine failure.

A temporary fix for the issue is by welding the flywheel with the shaft and getting it balanced and tried so that it does not wobble. 

The only true fix to this major engine issue is to replace the entire crankshaft assembly with an aftermarket one.

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Periodic Misfiring At Low RPM

Periodic and random misfiring at low RPM (1500-2000) and 1st gear is one of the common issues with the twin cam 103 Harley engine. There could be several causes for this issue and you need to cut out each to solve it.

Starting with the basics, check your fuel quality. Bad fuel quality often results in engine misfires, especially at low RPMs. Hence, you can drain out the existing fuel and load the tank with a fresh one.

Coming to the next cause, check out the plug wires, spark plug health, and tip to see if they are fouled or if they are too tight. 

You can try cleaning the spark plug or, rather, replacing it alongside the plug wire.

Fouled fuel injector could also be a potential cause for 103 engine misfires in Harley. Try out adding Chevron Techron (concentrated) 1.5 oz per gallon of fuel and run the engine at low RPMs.

Excessive Engine Overheating

The 103 Harley is a massive engine capable of producing a tremendous amount of power. But still, most 103-powered Harley bikes come with conventional air cooling technology. 

This flaw in the design causes the engine to overheat in a short time of riding the bike.

Try installing a wet-head if your engine is air-cooled and it may cool down your engine sooner and prevent overheating. 

Secondly, if the catalytic converter is located in the header pipe of the exhaust, naturally the engine would overheat.

To avoid this, it is advisable to install an aftermarket header pipe with no catalytic and tune it afterward. Moreover, it is recommended to give the engine first after riding for a certain period of time.

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How To Maintain The Harley 103 Engine?

Like every other motorbike engine, there are some basic tips and tricks to maintain the Harley 103 engine. 

This will increase the workability, performance, and lifespan of the engine and reduce the risk of any catastrophic engine failing issues.

  • Change the engine regularly and use accurate viscosity grade oil recommended by Harley Davidson.
  • Keep the engine clean and free from debris and dirt.
  • Monitor the engine temperature continuously on long rides and allow the engine to rest for a while.
  • Inspect for changes in the performance of the engine such as uncommon noise, low output, misfires, vibration, heat emission, etc, and address the issue accordingly.

Read Also: Harley Davidson 5 Speed Transmission Problems: Tips & Fixes!


Go through the following queries from Harley enthusiasts to learn more about the 103 engine issues.

How Much HP Does A 103 Harley Have?

There is no official information on the horsepower produced by the Harley 103 engine. But it can be estimated the twin cam 103 Cui can produce 65-85 HP which is variable depending upon the situation.

What Size Engine Is A Harley 103?

Harley’s twin cam 103 engine has a displacement of 1690 cubic cm, or 103 cubic inches. The 103 engine is rated at 100 lbs per ft of torque at 3500 RPMs.

Is The 103 Harley Engine Reliable?

Harley 103 engine has gained popularity due to its reliability and longevity. If maintained properly you can enjoy your Harley with a 103 engine for a longer time than expected and without any major issues.

What Is The Best Fuel For Harley 103?

Harley Davidson always recommends using first-grade unleaded gasoline for all of its engines including the 103. The best fuel for Harley 103 would be 91-95 grade unleaded Octane.

Final Words

No doubt the Harley 103 engine has great potential including some flaws like everyone’s machines. But keeping the bike maintained and tuned can give you a smooth engine performance for a long time.

Although some fixes to the Harley can be very expensive, such as replacing the chain tensioner and crank assembly.  It is better to do so in any way to keep the engine healthy and maintain the resale value.

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