5 Of The Most Reliable Harley-Davidson Engines Ever Built (According To Owners)

There are numerous ways to describe an engine. You can distinguish the best overall Harley Davidson engines, but constructing a list of the most reliable Harley engines is a different exercise in measuring longevity. Nonetheless, many of the engines on this list overlap with our picks for the best overall Harley engines simply due to their well-rounded designs. Perhaps reliability is an unintended consequence of power and speed, and fans of collectible Harleys will likely find their top choices among our most reliable picks as well. But whatever your approach to judging a motorcycle engine may be, there are some unavoidable criteria for deciding the best of the best.
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Our choices for this list are a bit more specific than those on our list of the best overall Harley engines. For example, the Milwaukee-Eight engine has been released in several different volumes — with 107, 114, 117, and 121 cubic-inch engines implemented in numerous Harley models. And for this list, we awarded the Milwaukee-Eight 114 the best-reliability accolade, since it’s the engine found on the wildly successful 2018 Harley-Davidson Fat Bob FXFB.
Our methodology in creating this list involved combing through owner reviews to discover the most commonly-cited engine models for their longevity. Power is still important, since a reliable engine should deliver its expected horsepower without fail. Secondly, determining reliability means a lower frequency of problems. If an engine has a pattern of complaints on sites like Motorcycle Reviews, it probably wasn’t a worthy choice for this list.
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