Why The Twin Cam 88 Is Considered One Of Harley-Davidson’s Worst Engines Ever

Harley-Davidson is a name that needs no introduction. Known for its American roots, plentiful customization options, and having a loyal fanbase, the brand has largely maintained a pretty good track record when it comes to build quality and reliability. With the Twin Cam 88 engine, however, many owners might disagree. As the successor to its Evolution engine, the Twin Cam 88 was used from 1999 to 2006, initially in the Dyna lineup, then later expanded to its Softail and Touring models. There were fundamental differences in this new engine not found in the Evo. 

Harley increased the size by 110cc, for a total of 1450cc, compared to the Evolution’s 1340cc. Other changes included a new camshaft drive system, which was now chain driven instead of gear driven, the oil system, crankshaft design, and more torque and horsepower without any modifications needed. Little did Harley know these upgrades would lead to common mechanical failures such as tensioner wear, chronic oil leaks, and other owner complaints that require expensive repairs.

One new change that is known to cause serious trouble with the Twin Cam 88 engine is its new cam chain tensioner, which tends to wear out and fail. If this happens, the tensioner shoe could disintegrate, causing catastrophic damage to your engine. Harley-Davidson recognized the issue and later introduced a tensioner upgrade kit. Despite this upgrade, another option is to just install a gear-driven kit instead, to avoid the problem altogether. 

Another likely complication has to do with the plastic oil pump gears in earlier versions, which are known to strip or break, resulting in a loss of oil pressure. However, there are recommended aftermarket metal gear upgrades you can find that will keep the system intact. Most 88 twin cam cranks are pressed together as opposed to being welded, making them prone to twisting when stressed. Any performance upgrades exacerbate the situation and will result in costly repairs. Leaking rockerboxes are also a subject of complaint, particularly with higher mileage bikes.

If you’re in the market for a Harley-Davidson or just bought one with a Twin Cam 88 engine, there are some things you need to know before making that purchase or needing an expensive repair. The years that are most prone to failure are from 1999-2002. These engines, referred to as TC88A, primarily suffer from plastic cam tensioners shedding into the oil pump, leading to massive engine damage. Models from Twin Cam 88s from 2003-2006 should also be avoided, citing that these models are risky without getting the crank inspected to make sure it’s been welded. 

In addition, it’s advised to ensure upgrades to the cam tensioner and oil pump have been done. Despite being replaced, Evolution engines had a simpler gear-driven, single cam setup and were highly modifiable. They were easier to service and more reliable for DIY project bikes. That doesn’t mean all 88s are bad; there’s just a process to owning one. Usually, if a vehicle has too many modifications, it’s best to be careful, but in the case of the Twin Cam 88, it’s pretty much a requirement.