103 to 117 big bore kit

The 103 To 117 Big Bore Kit – Is It Worth It?

Among Harley Davidson aficionados, a passionate debate continues to rage on the possibility of transforming an engine’s capacity from 103 cubic inches to 117 through big bore conversion. Such alteration could potentially deliver noteworthy increments in power and performance; yet carries several understandable difficulties and restrictions.

Main Issue #1 with the 103 to 117 big bore kit – Cost

Although a 103 to 117 big bore kit can give your Harley Davidson more power, the hefty price tag associated with it may be off-putting for many riders. Not only are new pistons, cylinder heads and camshafts pricey on their own, but you’ll also need to factor in labor costs for installation as well. This combination of high parts and installation fees makes this type of upgrade out of reach for some Harley fans.

Potential To Damage The Engine

When you opt for a 103 to 117 big bore kit conversion, the enlarged engine displacement can place intense pressure on the internal components, leading to premature wear and tear. Not only that, but it also intensifies stress levels on your transmission and drivetrain components – making them more prone to breakdowns or costly repairs. So if you go ahead with this modification, be sure you are prepared for any possible issues that may arise!

Why Do The Upgrade?

Despite the possible difficulties, many Harley Davidson owners prefer to execute a 103 to 117 big bore kit conversion. The main explanation for this is that the standard engine size of most touring models -103 cubic inches- can feel lacking in power by some riders. A117 cubic inch motor, however, brings an inspiring surge in torque and performance which leads to an altogether more thrilling ride experience for those willing brave it!

Several aftermarket companies offer kits that make the 103 to 117 big bore kit conversion far more convenient and cost-effective for Harley owners. These comprehensive packages come with all of the necessary components such as pistons, cylinder heads, and camshafts plus an easy-to-follow installation guide.

It’s essential to understand that a 103-117 big bore conversion is highly intricate and not something done in a few simple steps. It necessitates extensive technical expertise, specific tools, and the right equipment. Therefore, it’s advised to hire an experienced professional with a demonstrated track record for this job.

Is it better to just buy a 117 instead?

The decision of whether to buy a new 117 engine or undergo the labor-intensive 103 to 117 big bore kit conversion depends on numerous factors, including part and labor costs and the cost of purchasing an entirely new engine.

Converting your engine to a 103-117 big bore can be costly with both parts and labor costs steadily increasing. Furthermore, there is also the potential of causing irreparable harm to your engine during the alteration process – resulting in costly repairs.

On the contrary, buying a 117 engine can be an expensive endeavour depending on the motorcycle model and its availability in the market.

Comparing the cost of both options and evaluating their advantages and disadvantages is a wise approach before making any decisions. Additionally, it’s essential to consider the resale value when it comes to motorcycles – as adding 103 to 117 big bore kit conversions may not be as attractive for potential buyers as having a factory-built 117 engine from day one.

Generally, if the cost of converting your bike and purchasing a 117 engine are comparable, you may want to consider doing the conversion for its value. But in cases where the cost is significantly more than buying a new motorbike with a 117 engine already installed, it would be far more economical to just purchase one from the start.

My Opinion On The Conversion

From experience, if the costs are close, and even if the 117 is slightly more expensive, I would personally save myself all the trouble of going through the conversion process and just buy the 117 new. The only caveat to this would be if I already own a 103 and have customized it to my tastes already.


All things considered, a 103 to 117 big bore kit on Harley Davidson bikes is not without its hurdles and restrictions. Though the potential increase in power can be appealing to many Harley owners, it’s also crucial to take into account the cost associated with this alteration as well as the possibility of engine damage. As such, prior to making any decisions regarding this project, carefully review both its benefits and drawbacks while keeping price points in mind – preferably enlisting an experienced professional for help!


Below is a list of the most commonly asked questions related to the 103 to 117 big bore kit conversions for Harley Davidson bikes.

What is a 103 to 117 big bore conversion?

Experience a surge in power and performance on your Harley Davidson bike with the 103 to 117 big bore conversion. This upgrade allows for an increase of engine displacement from 103 cubic inches all the way up to 117, providing remarkable results that you’ll notice immediately!

What are the benefits of a 103 to 117 big bore conversion?

One of the key advantages of a 103 to 117 big bore conversion is an augmented power and torque that offers an exhilarating riding experience.

What are the downsides of a 103 to 117 big bore conversion?

However, there are some drawbacks to consider such as the hefty price tag as well as possible engine damage due to increased strain on its systems – from transmission and drivetrain components to internal parts.

How much does a 103 to 117 big bore conversion cost?

The cost of converting your 103 to 117 engine can vary significantly due to the parts and labor costs associated with it. New pistons, cylinder heads, and camshafts will accumulate in price quickly – as well as any required installation labor.

Can I do a 103 to 117 big bore conversion myself?

Although it is technically possible to complete a 103-117 big bore conversion on your own, it requires an extensive understanding of the tools and mechanics involved. Therefore, for the best results and quality assurance, this type of work should be handled by a professional with proven expertise in this field.

Are there any aftermarket kits available for a 103 to 117 big bore conversion?

If you’re a Harley owner searching for ways to upgrade your engine, then look no further! Aftermarket companies have put together kits that make the 103 to 117 big bore conversion process easier and more affordable. With these kits, all necessary parts are included along with comprehensive instructions on how to install them – making it straightforward for any enthusiast.

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