Why Did Harley-Davidson Switch to Timing Chains?

By Cameron Vanderhorst - January 18, 2021

Harley-Davidson switched from cam gears to cam chains on the Twin Cam motor at the turn of this century. Here’s why.

Harley-Davidson fans are among the most loyal motorcyclists of all. In addition, many are also fiercely loyal to the specific type of engine that powers their bike.

You’ll regularly meet Panhead loyalists, Shovelhead fanatics, and Twin Cam lovers who swear that their specific Harley-Davidson engine is the best one of all. When it comes to Evo fans, one reason many prefer them is reliability, thanks in no small part to the gear-driven camshafts.

After all, Sportsters still run gear-driven cams, while the bigger engines use cam chains. Why, then, did Harley-Davidson switch to a chain-driven setup? YouTuber GixxerFoo explains why in a recent video.

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He offers two possible reasons, both of which make perfect sense. For one, the Environmental Protection Agency was concerned with noise, and timing chains were one way to reduce engine noise. In addition, they were much cheaper to produce.

While we only the former to be true beyond a reasonable doubt, there are other cost-saving measures that took place throughout the Twin Cam’s run. It’s entirely logical that the switch to chain-driven cams was yet another cost-saving measure.

As Harley-Davidson engines grew larger and more powerful, the cam gears seemed like a worse idea. Machining a cam gear to be able to handle those higher power levels would have required far tighter tolerances – both on the gear and elsewhere – that would have driven manufacturing costs way up.

At the very least, each set of cam gears for each bike would require hand-fitting by the builder. This would add a lot of time to the assembly process, which, of course, costs money as well.

There is good news for Twin Cam fans. If you want, there are aftermarket kits that will convert your Twin Cam engine to run Evo-style cam gears. It’s a pricey upgrade and it requires a lot of mechanical know-how to install. However, the end result is glorious gear whine and more consistent timing.