Tech Tips

Changing the Top End Gaskets on Your Harley

Written by  May 31, 2005

After measuring up the tech tips that I have written, I was looking for a non-scheduled maintenance item that most Harley owners can handle. If you own a Harley with an Evolution engine, at some point you might notice that the top end is seeping oil. When this happens, you can either fix it or simply wipe the seepage away until a later date, preferably during the winter.

To make this repair, you must first locate the point of the actual leak. Washing the motor and applying baby powder to the area around the top end will help you accomplish this. If the leak is in the upper three gaskets of the top end, this can be done fairly quick, and requires you to remove the two half tanks and a few wire connectors that control the tank gauges. These are simple gaskets so don't be alarmed. They also have channels to fit the gaskets into, which makes this a simple task.

Removing the tank can be tedious due to the band clamps that Harley installs at the factory. I recommend that you replace the band clamps or use stainless steel hose clamps. The original clamps require you to use a tool that is normally used on CV shaft rubber boots in automobiles. CV shafts are front wheel drive axles for those of you who are not familiar with the lingo.

You must drain all of the fuel from both sides of the tanks and locate the bolts that hold the tanks together. After you have done this, and the tanks are free, you can set them aside in a safe place.

Now that you have exposed the top rocker arm covers, you can see the four Allen bolts you will need to remove to gain access to the gaskets you are about to replace. Before you attempt to remove the Allen bolts, keep in mind that these bolts are fragile, so be gentle when removing them so you don't break them off.

There are four gaskets that can be replaced on the Evo engine—the top cover, upper rocker arm gasket, middle rocker arm gasket and the hard one, the lower metal rocker arm gasket. This is why it is important to locate the exact location of the leak.

Removing the upper and middle gasket and the rubber breather is quite easy, however, the lower metal rocker arm gasket is a more difficult process because it requires the rocker arm assembly to be removed. Since the most common leaks are in the upper gaskets, I am not going to dive into the steps for replacing the lower rocker arm gasket. This is another topic in which I will go into further detail at a later time.

One thing I would like to stress is that you use original replacement parts for this repair. After cleaning and inspecting all parts, reinstall the gaskets and reassemble the components in the reverse of how you removed them.

Install the breather diaphragm that you received in the kit from Harley-Davidson, and install the top rocker cover. You must have the factory torque specs to accurately tighten the top four Allen bolts.

The rest is easy! Just reinstall the two half tanks, replace the fuel line clamps and connect the dash pin connectors. You will want to add fuel to the half tanks and check for leaks, then start the motorcycle and check for leaks again. If all went well, you should no longer have any leaks from the new gaskets you replaced. You have now stepped into another realm as a motorcycle mechanic, and you saved a lot of money! I score this as a 3 on the tough-o-meter scale.

The photos below should be self-explanatory and will guide you on this procedure.
If you need further assistance, this procedure is covered in-depth in the 1998-2004 Harley Davidson Factories FLH manual.

B-safe out there!

By Dave Miller