Jose’s XB Rocker Box Cover Upgrade for XL Engines  

 10/18/2008 16:32

Provided courtesy of Jose Quinones as posted on DC BRAG website

The primary benefit of  this upgrade is that it greatly improves the engine’s breathing ability and while reducing the amount of oil puking out of the heads, a subject near and dear to every Sportster/Buell owner. A side benefit is the “cool factor” of having new XB parts on you old tube frame Buell.

The pictures below helps to explain why this new cover works better than the old one. First,  you get rid of the spacer (and one more gasket that could leak),  eliminate  the tiny return hole (see #2 in diagram below) and replace it with a bunch of empty space in the top of the head. Second, the PCV valve is much larger than the original flapper valve enabling it to handle more volume in each head. Third, the air oil mixture only flows one way up through top of the head through the PCV valve. The old design had to go through a circuitous route (see diagram below), increasing the chances of oil pooling and puking when the engine decides to push the oil out of the breather bolt.


The Old Way


The New Way

Here are the parts that you will need:

17605-00YB - Rocker cover, front head $39
17642-02A - Rocker cover, rear head $39
17606-00YA - Grommet, Viton, Black $2.95 each (need 2)
17607-00Y  - PCV Valve, $6.90 each (need 2)
868A  - Hex Socket Button Head Screw, $4.75 each (need 2)


The only special tool that you really need is a cut down 3/16” hex wrench, shown below. Take a regular hex wrench and cut off about ½ inch of the short side of the wrench. This modification allows you to remove the hex bolts that are obstructed by the frame on the rear rocker box cover.

After removing the fuel tank take off the tie bars (top and the front) and the front motor mount.  This will allow you to rotate the engine down and away from the frame and give you more space to work in. Caution: Don’t forget to put a jack under the engine so it doesn’t drop on you when you undo the front motor mount. Slowly lower the engine using the jack until the motor mount gets close to the front tie bar frame member. I found that the extra space to work with was helpful.

The basic operation is  take off the four bolts holding the covers, remove the cover and the spacer, then install the new XB cover and bolt it down with the same four screws. The only two clearance issues that I ran into were the front cover and the front motor mount and the rear PCV valve and the Fuel tank.


Now, what do you do about the old breather holes in the head? Just use the two button head screws replace the old breather bolts, remembering to use thread sealant on these bolts.

For the front cover, I shaved away some material from the front left corner of the rocker box cover so it would clear the front motor mount during installation.  A friend of mine had cut down the edges of the head hex bolt in that corner to provide further clearance when removing and installing the covers. You can also completely remove the front motor mount, but I did not want to mess with it.

For the rear PCV valve, I found that by pointing it towards the rear of the bike and some creative filing there is just enough clearance between the top of the PCV valve and the bottom of the tank on my S3. I’ll keep an eye on this area to see if further modifications are needed.


 Finally, you can send the two hoses separately or tied together like I did into a catch can, or just into the ground like I did here, next to the oil tank drain. This will ensure that the side stand switch and hinge are always properly lubricated! 

So that’s it! The fun part now will be to see how long it takes your Buell friends to notice that your bike just looks “different” somehow.