5 Recent Bonehead Motor Company Mistakes Solved by the Aftermarket
Harley-Davidson is a very traditional company, and they typically don't make changes very fast or without a well thought out reason. Unfortunately, when they do make mistakes they can be slow to fix them, and the aftermarket usually figures it out first.
1. Cam Chain Tensioner - Early Dual Cam Motors
When the Twin Cam 88 motor debuted in 1999 they were the first substantial update since the Evo motor in 1984, and they were nearly universally loved. As the miles piled on, though, many people began to have premature failure of the oil pump, which quickly would destroy the motor. The failure was almost always proceeded by a "death rattle" from noisy, slack cam chains, but it usually happened so fast you couldn't even make it home before the damage was done. Turns out, the new cam drive system of 2 chains, 4 sprockets, and 2 spring loaded tensioners with hard plastic rub blocks had some issues. No one ever really determined if sometimes there were bad batches of rub blocks, or if the chains were rougher, or if it was heat or what. The fix (as seen on the right of the picture), originally designed by Andrews, then offered by Screamin' Eagle, is to replace the whole cam support plate with one that incorporates hydraulic tensioners that down push as hard on the rub blocks, which are also a different material. 2006 Dyna bikes and all 2007 Harley big twins got a factory version of this upgraded system.
2. Primary Chain Auto-Tensioner - Later Twin Cams
When the motor company fixed the cam chain issues on the 2006 Dynas, they managed to screw up the primary chain tensioner. Their newly designed, auto adjusting, tensioner would spring into position and had a ratchet mechanism to hold it there, to avoid the high spring loads that may have caused the cam chain issues. The problem arose as the primary chain and sprockets wore, and the miles rolled on, till the chain was no longer uniformly loose or tight. The chain would hit a loose spot, the tensioner did its thing, and the ratchet would hold it there, but now it was too tight at the tight spots. This really became an issue with the bike at 30,000 miles and above. Luckily, Hayden Enterprises already had the solution (installed in bottom picture), in their spring loaded chain adjuster without the ratcheting mechanism.
3. Weak Compensator - 2007-2011 Twin Cam Motors
The compensator is a part unique to Harley-Davidson motors, which smooths out some of the pulses to the primary drive from the big pistons firing. The basic unit is mounted to the end of the crankshaft, with springs and ramps that compensate for the irregular speed of the crank, and smooths the power to the primary chain. On bike from the mid-2000s to 2011, the stock unit just was not up to the task, as the twin cam motors made more power. In 2011, Harley upgraded the factory part to the Screamin' Eagle higher performance version, but many other aftermarket companies had already addressed the issue as well.
4. High/Erratic Idle - EFI Bikes
Electronically fuel injected bikes were a great leap forward from the old carburated motors, with the ability to compensate for temperature and altitude and deliver more power without running afoul of the smog police. The only issue was they were a little too perfect. The computer was constantly adjusting the running and would boost the idle to smooth out the engine with a little stepper motor. You couldn't adjust the idle speed, and a faster idle camouflaged the great irregular beat of the big twin motor when you were sitting at a light. Luckily the aftermarket (Idle King, American Motors, and others) stepped up with manual adjustment knobs to replace the stepper motor, which is easy to install and inexpensive. Unfortunately, they only work on the EFI bikes until the recent throttle by wire update.
5. Auxiliary Cooling Fans - All Years
Harley-Davidson makes traditional air cooled motors, with all those great looking cooling fins on a big V-twin under the tank. The problem is, the 21st century has a lot more stop and go traffic than the 20th, or even post-war 1960s America. A Harley will stay plenty cool cruising down the freeway at 60 mph, but drive the same bike into the city and you will start to feel the heat in your legs and the seat of your pants. The factory and the aftermarket first addressed this with heat deflectors, like the Crotch Cooler. A more technological solution was cooling fans to blow air over the fins at low speeds, like those from Love Jugs. Harley finally got with the program and started fitting their bigger touring bikes with fans and offering retrofits from Screamin' Eagle, but they don't flow as much air. Now, some 2014 and up Rushmore bikes incorporate small radiators in the lower fairing and circulate liquid coolant through the heads.
If you need guidance in installing some of these fixes, most are covered in the how-to section at HDForum.com
