Replacing the timing belt tensioners on a Harley-Davidson Twin Cam

The TwinCam 88 engines, which first appeared in 1999, are characterized by two camshafts (hence the nickname "twin-cam") and a double-eccentric oil pump in the same compartment. The crankshaft drives the oil pump via its shaft, and at the same time, via a chain, drives the rear camshaft, which in turn drives the front camshaft via another chain.

The tension of these chains is ensured by 2 mechanical tensioners , which act by the force of a spring.

Depending on the type of driving, the oil used, and the idle speed, these tensioners reach the end of their useful life as the friction material wears out, and they need to be replaced. If this maintenance isn't performed in a timely manner, they can wear out completely, eventually breaking and allowing the metal of the tensioner body to rub against the chain, producing strange noises and damaging the oil pump and engine in general.

This tensioner maintenance is not required on Dyna models from 2006 onwards and TwinCam 96 models from 2007 onwards, as the mechanical (spring-based) tensioners have been replaced with hydraulic ones, which last almost as long as the engine itself, so they practically do not require replacement.
Therefore, it is highly recommended to check the condition of these tensioners approximately every 40,000 kilometers to prevent further damage. If they are worn, we can replace them with the same part number, or, as in this case, upgrade them by installing a Screamin' Eagle kit. This kit converts our mechanical tensioners to hydraulic ones and simultaneously replaces the oil pump with a more modern unit, offering 8% more oil flow and 22% more return, increasing engine life and performance.

Safety first: Before starting, we'll disconnect the negative battery terminal to prevent the engine from starting unexpectedly. To begin the installation, we'll remove the fuel tank and rocker covers to release the rocker arms and relieve pressure on the camshafts. We'll do all of this following the kit's instructions and the manufacturer's service manual, which should always be in our toolbox.
Next, we remove the camshaft cover, which will give us access to the timing plate. Using a special tool, we release the tension on the chain tensioner.

Following the instructions, we remove this cover along with the oil pump and clean everything thoroughly. At this point, it's highly recommended to also replace the bearings holding the camshafts in the crankcase. The original HD bearings are manufactured by INA, but we can use better ones from Torrington (currently Koyo), which have more rollers and perform better.

Replacement requires the use of a bearing installer-uninstaller.

Before beginning component assembly, it is highly recommended to measure the crankshaft's rotation without deviation. This procedure will be performed using a dial indicator and checking the information in the service manual. Crankshafts in engines that have been over-worked may have runout, which could cause premature wear or breakage of the oil pump.

Once this check is complete, we proceed with the assembly of the components, always lubricating them with special assembly oil. Our service manual will guide you step by step through the entire process.
Special care must be taken when aligning the pump with the crankshaft, tightening the bolts in the order indicated while turning the engine with the rear wheel. After this, we will check the alignment of the timing sprockets so that the chain runs quietly and centered.

We then tighten the bolts holding the pinions, and we can now install the cover with a new gasket and proceed with the assembly of the pushrods and rocker arms. After installing the rocker cover and the reservoir, we remove the spark plug wires and crank the engine a few revolutions to fill the new pump with oil. We reinstall the wires, start the engine, and after checking that the oil pressure light goes off and the engine runs quietly within a few seconds, we can perform a road test.

Frank Burguera

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