How to Replace Harley Rocker Box Gasketsby Don Davis
Leaking rocker box gaskets were a particular problem with Harley Evolution engines. Harley went through four generations of lower rocker covers and four versions of the middle cover, or D-Ring, as the motor company tried to solve the problem. The earliest gaskets, from 1984 to 1987, were made of cork. The next versions, which lasted until 1990, were made of zinc and leaked the most. Subsequent versions were rubber. Removing rocker box covers to replace the gaskets is a straightforward process. Very experienced mechanics can do the job without removing the gas tank but less experienced mechanics should probably begin this job by remove the tank.
Close the petcock. Ensure the motorcycle is cold.
Remove the seat bolt and washer from the tab on the rear of your seat. Remove the seat to access the battery. Loosen the negative battery cable from the terminal with a box wrench and remove the cable from the battery.
Remove the center console. Typically, the center console is attached to the center console bracket with three Allen head screws.
Remove the fuel line from the petcock. Typically the petcock and fuel supply are joined by a hose clamp. Loosen the hose clamp with a flat head screwdrivers.
Drain the gasoline in your tank into an adequately sized, sealable, gas can. On models with dual gas caps, disconnect the crossover and fuel venting hoses in the front, middle bottom of the tank.
Remove the front mounting bolt, flat washers and acorn nut with a box wrench and socket wrench. Remove the rear mounting bolt, flat washers and acorn nut.
Disconnect the fuel gauge connector on recent models. The fuel gauge connector is under the left side of the fuel tank.
Remove the gas tank from the motorcycle. Set the tank on a flat stable surface in a well vented place.
Remove the six Allen bolts and washers that connect the rocker cover to the rocker assembly. Begin with the front rocker box and work on one cylinder at a time.
Remove the metal D-ring if your motorcycle is equipped with an Evolution engine. Note the top, bottom and orientation of the D-ring. Completely remove the old gasket. Use a gasket scraper if necessary.
Examine your rocker arm housing. Rocker arm housings with only a partial inner lip require you to use an adhesive like high temperature rubber cement to properly install the new gasket. Rocker arm housings with a full inner lip do not require adhesive.
Apply adhesive if needed and properly place the gasket on the rocker arm. Replace the D-Ring on Evolution engines. Replace the rocker arm cover.
Tighten the Allen bolts in a cross pattern to 10 to 12 foot pounds of torque. Refer to the shop manual for your motorcycle and use the exact torque sequence and specifications described there.
Re-bolt the gas tank to your motorcycle. Reconnect the fuel gauge connector. Reinstall the fuel line to the petcock.
Reinstall the center console. Refuel the motorcycle.
Reconnect the negative battery cable to the battery. Reinstall the seat.
- Woodring, Kip and Love, Kenna; Harley Davidson Performance Projects: Sealing Your Rocker Boxes
- Clymer Harley-Davidson Twin Cam 88 Service Repair Maintenance, Rocker Arm Assembly, pages 106 -107
- Harley-Davidson Service Manual 2005, Fuel Tank Removal Section 4.7, page 17
Things You'll Need
- Allen wrenches
- Gas can
- Box wrenches
- Socket wrenches
- Gasket scraper
- High temperature rubber cement
- Service manual for your motorcycle
- Torque wrench
Don Davis has been a professional writer since 1977. He has had numerous writing jobs, including writing news and features for the "Metrowest Daily News" and "Los Angeles Herald-Examiner." Davis has a Bachelor of Arts in English and history from Indiana State University.