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If you're wondering if the installation of your engine kit is within your abilities, read on. Thousands of people with little or no prior experience working on Harleys have
successfully installed engine kits in these bikes. They're really a very simple engine to work on, and the pushrod valvetrain and air cooled design both simplify the disassembly and reassembly of
the top end. If you have the tools you'll need, and you can read and follow directions, are reasonably patient and careful, you can do this yourself and save a lot of money.
So let's get started. The following tutorial is oriented toward the XL engine, but 99% of it applies to Big Twins as well.
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Gather the needed tools and supplies. Here's what you'll need:
- A Factory Service Manual. Don't scrimp on this, it's important. Get a genuine HD version, they're the best
- Common hand tools, including 1/4" and 3/8" drive socket sets (english), a hex key set (better known as allen wrenches), an assortment of screwdrivers and pliers.
- A torque wrench that works for inch-lb ranges. You'll be torquing fasteners as light as 90in-lb. Generally speaking, either a 1/4" drive or a smaller 3/8" drive torque wrench is ideal.
- A torque wrench for torquing the head bolts, which are torqued in steps from 9ft-lb to 42ft-lb. We recommend a larger 3/8 drive torque wrench for this. You're operating
too far down the range if you use a 1/2" drive torque wrench. Pick up a 1/2" 12 point socket for this torque wrench, along with extensions of various lengths. A swivel adapter can be handy too.
- A 5/16" T-handle hex key wrench (Allen) with a ball end and a long shank is a great tool for removing the upper manifold bolts. Bondhus offers a T-Handle set that's reasonably priced and works great.
- A 5/16" L stubby type hex key wrench (Allen) will be needed to remove the lower manifold bolts. Many people cut down a standard L wrench. Bondhus makes a really nice set of stubby wrenches though.
- Shop towels (common blue shop paper towels available almost everywhere work well) and brake parts cleaner are good things to have handy.
- Engine assembly lube. We recommend Red Line assembly lube and we have it available.
- A medium file and a set of feeler gauges for gapping your rings (not needed if you purchased the pre-assembled option from us).
- A piston ring expander, for installing the rings onto the piston. A cheap but effective one is available at Sears (not needed if you purchased the pre-assembled option from us)
- Some way of supporting the back of the bike such that the back wheel is off the ground. A jack type bike lift or swingarm stand works great for this. You can improvise with a milk crate if you get
someone to help you lift the bike onto it. But you'll need the back wheel off the ground and the ability to turn it.
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- Disassemble the top end. This will vary somewhat from bike to bike. Consult your service manual, it's your best source of information. Here are a few tips though that may not be in your service manual:
- Remove the spark plugs before attempting to rotate the engine.
- Rotate the engine using the back wheel, with the transmission in top gear
- Be sure the engine is rotated to the valve closed position before attempting to loosen a rocker box. This will remove the valve spring pressure from the rocker box and prevent possible damage. To make sure
the valves are fully closed, rotate the motor forward while watching the intake rocker. When you see the intake valve open, and then close, the next occurence of TDC on that cylinder is a good place to stop.
Check piston position using a tie-wrap, straw, or similar soft object held through the spark plug hole.
- When it comes time to remove the pistons, first place rags under the pistons to eliminate the possibility that your wrist pin circlips might fall into the crankcase.
- You'll probably find that the wrist pin does not want to slide out easily. The best solution for this is to use a wrist pin puller, but if you don't have one, the pin can be carefully tapped
out using a small hammer and a punch. It's very important that your tapping does not get transmitted through the connecting rod! Doing so can damage the rod and/or the big end bearing. Have one
person support the piston while another person taps very lightly from the opposite side. Be patient, don't hit it hard.
- Gap your rings.The rings we provide in our engine kits are file-to-fit, meaning you must set your ring gaps before installation. Note that we offer the option of performing this service for you when you purchase
one of our engine kits:
- Clean your pistons and rings thoroughly using the brake cleaner. They are filthy as they come out of the packages (even if they don't look it) and you need them to be spotless.
- Clean your new cylinders thoroughly using soap and hot water. Dry them completely.
- Start with the oil rails. Reference the instructions, but the oil rail gap typically has a very wide tolerance, anywhere from say .015" to .050" is a common spec. Square the oil ring
in the cylinder at least 1/2" down from the top. Resist the temptation to do this right at the top of the cylinder to simplify squaring the ring, you must check all rings at least 1/2" down the bore
for accuracy. Do not check ring gaps in the spigot end of the cylinder, it is notorious for distortion due to the lack of material backing it up. Check ring gaps from the top of the cylinder only.
It takes very little variation in bore size to cause a large variaton in ring gap so using a place that's round even in an unstressed cylinder is critical. Ideally you'd even clamp the cylinder
in a torque plate to simulate the stresses of an assembled engine, but 1/2" to 1" down from the top on an unstressed cylinder is a good place.
- In the unlikely event that the oil rail gap is too small, you probably won't have much success filing it wider. Instead, just touch one end of the rail to a grinder. Then deburr it well using a file,
you do not want any burrs on the rings.
- Once the oil rails are ready, assemble the expander and oil rails on the piston, orienting the gaps per the instructions. Take great care to avoid overlapping the ends of the expander, they must
butt up to each other. Double and triple check this.
- Identify the second ring. It will most likely have a marking to indicate which side goes up. The instructions that come with the rings will have this information, as well as suggested ring gaps
for various applications (gasoline, nitrous, nitro, etc) and bore sizes. If you're not sure on the ring gap, call us to consult. Place this ring in the bore near the
top of the cylinder. Put the piston into the cylinder upside down, and push the second ring down the bore. The piston will stop at it's oil ring. An inverted piston with oil rings installed like this
makes an excellent ring squaring tool. Measure the gap using the feeler gauges. To adjust the gap, clamp your file into a vise and squeeze the two ends of the ring against the file while moving it
back and forth. Be careful, don't overshoot your desired ring gap! Keep the two ends of the ring parallel and square to each other as well, don't allow them to file into a "V" shape or lean to one
side or the other. When you've achieved your final gap, very carefully deburr all four edges of both ends of the ring, using your file. This step is critical! Rings must be able to move freely in
the ring groove, any burrs will inhibit that movement. Clean the ring thoroughly after all filing operations are done. Don't put it on the piston yet, you'll need the piston with just the oil
ring to use as a squaring tool for the top ring.
- Repeat the above for the top ring.
- Install the second and then top rings onto the piston using the ring expander. Be very careful not to scratch the piston along the way. Make sure the rings move freely even when the ends are tucked into the groove.
Orient all gaps per the instructions. Double check that the top and second rings have their dot markings up. Triple check this, it's not a mistake you want to make.
- Repeat the above steps for the other piston and it's rings.
- Preassemble your pistons into the cylinders. Again, this is offered as an optional service, together with ring gapping, when you buy an engine kit from us:
- Put one of the wrist pin circlips into it's groove in the wrist pin hole. Make sure it's fully seated in it's groove.
- Clean the anti corrosion coating off the wrist pin using some brake cleaner, lubricate it with assembly lube, and insert it into the wrist pin hole.
- Identify the cylinder to be installed as either a front or rear. In most of our kits, the cylinders are identical and can be installed in either position. However, on larger bores in particular,
the cylinder may have a clearance cut on it's spigot that needs to be oriented to the intake side.
- Turn the cylinder upside down and on a soft rag to avoid scratching the head gasket surface.
- Smear liberal amounts of assembly lube onto the rings and the piston skirts. Try to avoid getting lube onto the piston above the top ring.
- Place the piston top into the spigot and let it rest on the top ring. With most of our kits, the piston can be installed either way. However, if you have one valve pocket that's larger than the other,
that valve pocket needs to be positioned to the intake side. Likewise, if there is any kind of a clearance cut on the piston skirt, that side needs to be
positioned to the intake side.
- Carefully work the top ring into the spigot using your fingernails. If you need more pressure, use a piece of hard plastic, never use anything made of metal. The blunt end of a Bic pen works well.
Do the same for the second ring and finally the oil ring
- Push the piston into the cylinder. It should have normal resistance from the friction of the rings against the cylinder wall. If it take excessive force, pull it back out and investigate the possibility
that an oil ring came out of it's groove and got sandwiched between the piston and cylinder wall. It's rare, but it can happen. Another possibility when the piston does not want to push down
is air trapped between the piston and the rag under the cylinder. You can put the cylinder dowels in place to avoid this.
- Apply assembly lube to the cylinder wall liberally.
- Turn the cylinder right side up and push the piston down the bore. Using a clean shop towel, wipe any assembly lube off of the cylinder wall. The cylinder wall below the piston is lubed well but above the
piston should be free of any lube
- Repeat the above steps for the other cylinder.
- Install the cylinders and pistons:
- Thoroughly clean the base gasket surface on your engine cases. Try to avoid scratching it.
- Place your new base gasket over the cylinder studs and slide it down to the crankcase. Make sure it's oriented correctly such that the alignment dowel goes through the appropriate hole in the gasket
and the oil drain hole in the gasket is situated over the oil drain hole in the crankcase.
- Rotate the engine so that the connecting rod is about halfway up.
- Carefully push the piston down such that wrist pin hole clears the spigot. Do not push it farther or the oil ring will be at risk of popping out of the spigot.
- Push the wrist pin halfway out such that the area between the wrist pin bosses is clear.
- Carefully place the cylinder and piston assembly over the cylinder studs and slide it down. Have one person hold the cylinder while the other person puts the top end of the connecting
rod into position and slides the wrist pin through.
- Carefully install the remaining wrist pin circlip. Be absolutely sure it's fully seated in it's groove! That is not a mistake you want to make. Double check this. Triple check this. When
you'd be willing to bet your life that both clips are fully in place, push the cylinder down over the piston and onto the crankcase.
- For holding the cylinder down while you turn the motor to position it for the installation of the other cylinder, some 1/2" PVC unions and your shorter head bolts work well. The PVC will not damage
the cylinder deck surface.
- Repeat the above steps for the other cylinder.
- Install the heads:
- Place the head gasket onto the cylinder. If you're using a multi-layer steel gasket that's held together with rivets, look carefully at the position of the rivets. Any rivet that may
get sandwiched between the head and cylinder will need to be removed. They're very easy to remove using a bench grinder, simply grind away the entire tab that contains the rivet and deburr.
- Also note that multi-layer steel gaskets do not use o-rings around the alignment dowels the way the factory gaskets do. If you install o-rings on the dowels with a multi-layer steel
gasket, you guarantee yourself a leak.
- Very carefully place the head over onto the cylinder and gasket, taking care not to scratch the deck.
- Lube the threads, shanks, and undersides of the heads on the head bolts and install finger tight. Torque in the order shown in your service manual. For multi-layer steel gaskets,
torque all head bolts to 9ft-lbs, then 14, 22, 35, and finally 42ft-lbs. For composition type gaskets, follow the procedure described in the manual.
- Clearance the rocker boxes:
- This step is not described in your factory service manual simply because with all stock components, there's plenty of clearance. But it's incredibly important on a performance build.
It's not optional! Unfortunately, it's also one of the hardest steps to get people to pay attention to, and believe it or not, we have more trouble with professional mechanics
skipping this step (or taking it lightly) than with the backyard tinkerers, because the pros tend to think they already know how to put on a rocker box. Take this seriously please!
- The most critical clearance in the rocker box is the clearance between the valve springs and all areas of the rocker box around it. If the valve spring or retainer is allowed to touch the
rocker box, it forces the valve to land sideways on the seat. This causes seat recession and the resultant loss of seal, which of course saps power among other things. Performance springs
are larger in diameter than the factory springs and they will generally want to touch the rocker box. You absolutely must provide a minimum of .025" of clearance all around the valve spring
and retainer. Grind or file on the rocker box as needed to achieve this clearance. Note that with a beehive spring pack, this probably won't be an issue, but check it anyway. With
a conventional straight wound performance spring pack, it will almost certainly be an issue.
- The other rocker box clearance to look at is the clearance between the rocker arm and the underside of the rocker box cover. With high lift cams, the rocker arm will often make contact
with the rocker box top, which not only causes noise, but can cause leaks as well. Use a little play-dough or modeling clay to check this clearance.
- Finish the assembly. For the remainder of the assembly, you should follow the factory service manual. Here are a few tips that you may not find in it though:
- Place a little assembly lube on the valve stem tips and tops of the pushrods prior to installing the rocker boxes.
- It's very important to position the motor correctly before attempting to install a rocker box. Not only must the motor be at or near top dead center (TDC), but it must be at the correct TDC.
A four stroke engine makes two complete revolutions to complete it's cycle, and therefore the piston passes through TDC twice. One of those times is overlap TDC, which has the valves slightly
open. You do not want to remove or install the rocker box with the motor in this position. Turn the engine one complete revolution from overlap TDC to get to compression TDC. Both valves are
closed at compression TDC, so this is the position you want to install the rocker box. An easy way to tell if the motor is at TDC is to turn it forward while watching the intake lifter
or pushrod. You will see the lifter or pushrod go up and then down again. The next TDC that occurs after it goes down is compression TDC.
Thoroughly oil the valve springs and rocker arms after you've torqued the rocker box down. Pour engine oil all over them, and also over the pushrod end of the rocker arm, allowing oil to flow
down the pushrod tube. It takes awhile for oil to get to the top end, and you do not want it running dry while the oil is making it's way up there.
- Do yourself a gigantic favor and replace the two lower intake manifold bolts with hex head bolts, so that you can easily get to them with a standard wrench. The size you want is 5/16-18 x 3/4.
- After assembly, but before touching the starter button or installing spark plugs, turn the motor over using the rear wheel through two full revolutions of the crankshaft to check for any mechanical
interference of components. The starter is very unforgiving and it will damage parts if something is amiss. If you feel any mechanical interference, disassemble to investigate the root cause.
- Proper break-in is critical to realizing maximum life and performance of your engine kit! We can't stress this enough. Follow these steps to the letter. Ignore any alternative methods you may read about
on the internet!
- Make sure that your jetting or injection mapping is safely on the rich side and your ignition timing is set for no more than 28 degrees of total advance (23 degrees on dual-plugged motors). Use
a cold heat range spark plug such as an HD 10R12.
- Minimizing heat is absolutely essential to successful break-in, and excessive heat will damage your pistons and forever condemn your motor to be a mediocre performer. The reason for this is that
neither your rings nor your cylinder bores are perfectly round on initial assembly. Therefore, the rings are actually only making contact with the cylinder walls in a few places. The tension of
the rings is concentrated in these places, increasing friction and heat. This condition exists until the rings have a chance to carve the cylinders into their shape. While that process is taking place,
however, the rings and the pistons are very vulnerable to damage from excess heat. You can learn more about this phenomena by researching "ring microwelding". It's a very real risk to your engine!
- The assembly lube you put on the rings and pistons is to help combat ring microwelding. Yes, we know that some shops recommend minimal or even no lube at all to better assist the break-in
process. We don't subscribe to that theory. Your rings are at much greater risk of microwelding than they are of failing to seat. They will seat just fine. You need to pay attention to the possibility
of damaging them.
- On your initial start-up, run the engine no longer than 10 seconds. Use a clock with a second hand or a stop watch. Don't guess! Shut it off and allow it to cool completely to room temperature.
A little bit of patience now will go a long way to providing you with a strong motor that lasts a long time.
- For your second heat cycle, run the motor no longer than 20 seconds. Again, time it properly, don't guess. Allow it to cool completely.
- Repeat these heat and cool cycles with run times of 30 and 40 seconds.
- You're now ready for your first ride. Keep the rpm's down as much as possible and keep air flowing across the cylinders. Ride it no more than a mile, shut it down, and let it cool completely
- For your second ride, treat it similarly gently. Keep your rpm's below 3500 and keep air moving across the cylinders. Ride it a couple miles and let it cool completely.
- For the next 50 miles, do not exceed 3500rpm and avoid using full throttle. Vary your speeds, allowing the engine to pull and then decelerate gradually. This reversal on the rings, from pressure to
vacuum, assists in the seating process.
- For the next 500 miles, stay below 4000rpm, avoid using full throttle, and keep the heat down. You are now ready to enjoy the full power of your new engine kit
- Have your bike professionally dyno tuned. Proper tuning is critical to maximum power, long life, and good gas mileage. It makes no sense at all to spend thousands on motor work and then
leave power on the table, and put it all at risk, because you didn't spend a couple hundred on a proper dyno tune.
- More things to know:
- Optimizing your squish clearance (the clearance between the piston and the head as the piston passes through TDC) can reap benefits in the area of power, efficiency, and detonation resistance.
Check the Tech Tips section for an article on how to go about setting your squish clearance.
- High lift cams require special clearancing procedures in the cam box and may require special tappets with longer anti-rotation pin flats for extra tappet pin clearance. Likewise, cams with high
TDC lift figures (symptomatic of high amounts of overlap) will require piston to valve clearance checks. Refer to the appropriate Tech Tips article for more information, or call the shop with questions
- High lift and/or high overlap cams also require special clearance checks in the cylinder heads themselves. If we prepared your heads for you, and you told us what cams you're using, you're good
to go, we've set them up. But if your heads are not prepared for high lift and/or high overlap, you run the very real risk of problems like coil bind, valve to valve contact, or retainer to
guide seal contact.
- The above instructions are tailored for a person installing an engine kit at home, who may not have specialized tools like ring compressors, filers, and the like. As such, these instructions deviate somewhat
from procedures you may find elsewhere. We've found the techniques described above to be effective and safe, however.
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