Doing your own maintenance and repair on your motorcycle can be rewarding and save you money. However, you must take the time to do the job correctly. While some fasteners may not require such precise measurements, you must tighten the intake bolts to factory specifications -- too loose and you will compromise performance, too tight and you might strip the threads in the engine head.
Failing to tighten your intake manifold to specifications can cause poor idling, poor acceleration, hard starting, poor performance on the road and poor high-speed performance. These problems result from a lean fuel-to-air mixture, meaning too much air enters the combustion chamber.
Types of Intake Manifolds
A Harley-Davidson twin-cam engine can have one of two types of intake manifolds -- one for a carbureted motorcycle and the other, for a bike with electronic fuel injection, called an induction module. Harley-Davidson began offering electronic fuel ignition as a standard feature on its twin-cam engines in 2007.
Carbureted Twin Cam Torque Specifications
The intake manifold on Twin Cam engine with a carburetor requires tightening to a torque of 15 to 17 foot-lbs. Install the manifold mounting screws hand tight at first, and don't torque them down until after you've installed the air cleaner back plate.
Fuel-Injected Twin Cam Torque Specifications
The induction module on a fuel injected twin-cam engine has the same torque specifications as the intake manifold on a carbureted engine: 15 to 17 foot-lbs. As with the carbureted model, do not tighten the manifold mounting screws until you have installed the air cleaner back plate.
- "ctory Manual"; Harley-Davidson; 2001
- "Clymer Twin Cam Maintenance, Troublehsooting and Repair Manual for the 88 & 103 Cubic Inch Engines"; Clymer; 2005
- Photo Credit gros plan du moteur d'une moto de lÃ©gende image by ParisPhoto from Fotolia.com
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