Top End Removal
In this video, Mike Roen takes us through Harley top end disassembly on a Twin Cam. As always, review your service manual before attempting a labor intensive job, such as this. Also, refer to your manual as you work.
It is important to have a clean, safe area prepared for disassembly. The motor may be apart for at least a couple of days, especially if you are sending heads and cylinders out to a machinist.
It is important to clean and lay out all of your hardware and parts in such a manner that you will be able to easily identify and remember order of reassembly.
Not Your Everyday Harley Project
There are a few reasons for disassembling your top end. Freshen up a motor: With high miles, a motor may have excessive carbon build up on the pistons or in the heads. Gaskets may need to be replaced as they begin to fail and allow oil to seep past. Performance upgrade, often a rider will be looking for more horsepower and opt to build a bigger motor or build for more compression.
Getting Into The Harley Top End
You will start by removing the battery negative cable, fuel tank, and exhaust. Remove the top motor mount; including the horn assembly. In the same area; remove the fuel line and the engine temp sensor. Next, remove your air cleaner assembly, throttle cables, and carefully, unplug all of the sensor plugs at your throttle body. You can take a photo, or label these sensors and corresponding plugs, but every plug/sensor has its own specific plug configuration and is almost impossible to mix up. Now, you can remove the hardware that secures your throttle body to the heads and carefully slide the complete throttle body away from the motor.
Harley Rocker Box
You may want to remove your coil mount & coil so that you have more room to remove your front rocker box. If you do, be sure to label the coil and wires; front & rear. This is very important for the single fire ignition. The plug wires can not be mixed/changed. It is a good idea to use a piece of tape to label your rocker box uppers and lowers; (label) front & rear. These pieces can be swapped front to rear / rear to front; but it is good mechanical practice to put the same components back in their original locations, especially for consideration of components wearing together. Loosen and remove your upper rocker box.
Now is a good time to remove your spark plugs, raise your rear wheel and shift the motorcycle into high gear. You will want to spin your rear wheel until you have reached top dead center. At this point there is the least amount of pressure on your pushrods which allows for ease of disassembly. Remove your pushrod clips. Next, loosen and remove the two bolts that retain your breather assembly; then evenly, loosen and remove your rocker arm towers. Label the towers front and rear and set them aside. Label your pushrods FE, FI, RI, RE (front exhaust / front intake / rear intake / rear exhaust) and set those aside. Now, you can loosen and remove your lower rocker boxes. You are now stripped down to the heads.
Loosen Head Bolts
You will need a 1/2″ 12 point socket to loosen your head bolts. Break them free with one sharp motion; then continue to loosen evenly in a cross pattern. Lift off your heads and remove the old head gaskets. Next, you can carefully slide the cylinders off of the pistons and cylinder studs. Work slowly and methodically. Focus on not allowing any debris to enter the open crank case. Label the cylinders and set aside. Now you can push clean shop towels into the openings of the crank case to protect against anything falling into your lower end, while the top end is apart.
Protect Cylinder Studs
Finally, you can remove your pistons from the connecting rods. It is important to slide short lengths of rubber hose over your cylinder studs for protection. Then, proceed by picking out the wrist pin clips and carefully tapping the wrist pins out from the connecting rods. It is preferable to use a connecting rod holder when tapping out the wrist pins, if the tool is available to you.
Harley top end overhaul is a lengthy procedure on your Twin Cam motor. Follow Mike’s instructions and refer to your service manual. You will see that a lengthy job does not necessarily make it a difficult job. By taking your time, focusing, working clean and orderly, you will find yourself moving right through this detailed repair or upgrade.
Time to put it back together.