EVO: Engine Mechanicals

Timing Inspection Hole


Motor Mounts

Comparing 03-04 Style Front Mounts

The pics below show the difference between the 2003 and earlier front engine mount and the 2004 and later.
Note that the right head mount is inward about 1/4“ on the newer mounts.
Older mounts could be easily modified to work on 04 and up models.

03 (black) and 04 front engine mounts. 1)

Cylinder Mounting Studs

Weakest cylinder mounting stud holes in the case. 2)

Cam / Gearcase Cover

Removing the Cam Cover

  • Checklist:
    • You'll need to bleed down the lifters and loosen or remove the rocker boxes:
      • Pulling the cover without first loosening the rocker boxes to take the pressure off is generally a bad idea.
        It's hard on the cam bushings to have valve spring pressure pushing down on them while the cams are only supported on the inboard side. 3)
        See the links above for removing the rocker boxes prior to removing the cam cover.
      • The rocker box puts downward pressure thru the pushrods / lifters to the cams and subsequently the cam bushings.
      • The bushings are then pressed hard against the cover in which the bushings reside. Kinda like holding your arm down on a table and let someone push down on your arm.
        Then try to pull your arm away. It's harder to do.
      • Without relieving that pressure, pulling the cover off can let the front of the camshafts fall down.
      • This throws all that weight on the bushings inside the case that the other side of the camshafts are in.
      • At this point, the camshafts are sitting in there at an angle waiting to tear into the bushings.
      • This can destroy the bushings in the case.
    • To bleed the lifters respectively on each cylinder:
      • The first side, say the front, spin the engine around by rotating the tranny in high gear until you see both valves come up and back down.
      • Pull the spark plugs.
      • Rotate the engine through the intake cycle:
        • Watch the pushrod end of the intake rocker arm as you're rotating the engine forward.
        • You'll see the intake rocker move up and open the valve.
        • Then you'll see the rocker lower and close the intake valve.
        • When the intake valve closes during rotation, both valves will stay closed for a bit on further rotation.
        • As long as you stop on a point where both valves are closed it's fine.
        • That puts the lifters at there lowest point (on their base circle) and their least amount of pressure against the bushings.
        • You can also have a helper watch for the TDC line to appear in the center of the timing hole with the plug removed (if applicable).
      • Now, walk away for 20-30 minutes while the oil slowly gets pushed out of the lifters at this point.
        ——————— waiting ———————
      • Then remove the lower rocker box on the front head.
        (you can leave the rocker box sitting on the head but remove the pushrods to move that aspect off the cams)
      • Place the pushrods away in a safe place and mark which lifter each came from.
      • You can remove the pushrods before removing the lower box so you don't have to pick it up over them.
      • Next, repeat the above for the rear cylinder.
      • Now the pressure is off the cam bushings and it's a lot easier and safer to remove the cover.
  • The cam cover has 11 Allen head screws of various lengths.
    They will need to be replaced back in the same holes from which they were removed.
    So, their proper location will need to be marked upon removal.
    You can make a drawing of the cam gear case on a piece of cardboard.
    Then put them into the cardboard in the proper orientation as removed from the cover. 4)
  • Although it may not be necessary and depending on your foot control setup;
    You may have to remove the foot peg / foot brake pedal support or brake rod to fully remove the exhaust or cam cover.
Remove the exhaust. 5)Place a flat drip pan or container under the engine to
catch any oil leaking out. It will leak oil when the
cover is removed. 6)
Remove the Allen screws holding the cover on and
place them in holes cut into a piece of cardboard for
safe keeping and sorting of various length screws. 7)
  • Pull the cover out slightly so that it un-attaches itself from it’s gasket and the engine case.
    • Note: The bushing alignment with the camshafts has a VERY close tolerance.
      That means that the cover will need to come straight out.
      There will be no side-to-side or up-down play in the cover.
  • You may need to lightly tap the sides of the cover with a rubber mallet to break the seal between the case and the cover.
  • Note: It's best to try and keep the cams in the gearcase while removing the cam cover.
    • It's possible that the cams will stay in the engine when removing the cover.
      However, more often than not, they will come out with the cover in various ways.
      The alternative to not paying attention to them may end up with the cams hitting the floor.
      Or worse, them hitting something on the way down causing damage to them.
    • Nicked journals will destroy the bushings, nicked lobes will destroy lifter rollers and both will create extra heat, destroying the cams and other internal parts.
    • With the cover out far enough to get a small screwdriver or putty knife between the cover and the case,
      Continually push the cams back in towards the engine as you slowly edge the cover off starting with #2 cam.
    • #1 and #3 cams are behind #2 and will go back when you nudge #2.
    • Don't forget about #4 which is independent and can come out on it's own.
  • Once the cover bushings are clear of each cam, the case can be slightly rotated out of position.
  • Also, you will need to remove a rubber oil line that attaches to the rear area of the case before the case can be completely removed.
    Since the clamp holding this oil line cannot be reused, you will need to purchase a new hose clamp when the case is re-installed.
  • Remove and discard the gasket. Clean the case with brake cleaner.
The cover should come off slow with even pull applied and all cams safely in the case. 8)At this point, you can use a screwdriver or putty
knife to push the cams back in the case 9)
This is what happens if you don't remove the
inspection cover and / or the rotor cup bolt from
#2 cam before removing the cam cover. 10)
This is what can happen to the cams positioning if
you try to re-install the cover with the cams still
attached to it. 11)

If you plan on leaving the cams in the case while working,
It's a good idea to secure the cams with string or rubber bands across #2 and #4 cams to keep them from falling out.

Securing cams with rubber bands 12)

Cam Cover Seal

Seal number (11124):
This surrounds and seals #2 cam when the cover is installed.

Removal / Installation

Using a screwdriver and hammer, insert the screwdriver inside the lip of the seal from the rear of the cover.
Knock the seal out of the cover. 13)

Clean the recessed area for the new seal thoroughly.
You can use compressed air or brake cleaner (cover the ignition if still installed). Set the new seal over the hole aligning it as straight as possible. 14)

Use a socket and a hammer to drive in the new seal straight to the cover.
The socket O.D. needs to be just smaller than the seal.
Make sure the seal is flush to the cover when done. 15)

Installing the Cam Cover

The cover gasket only has a hole for one of the dowel pins so it will slip down if you're trying to place it on the case first.
Put the gasket on the cover and install the screws through the cover and the gasket holes while maneuvering the cover on the case.
Hand start all the screws and leave it loose enough to nudge the gasket, if needed, for a good fit.
This will keep the gasket from sliding down during the process.

Or you can use a few plastic straws inserted into the case threads and put the gasket on the case over the straws.

You can also buy a short piece of 1/4”x20 all-thread at the local hardware store and use it the same way as the straws.
The cover is app. 1-1/4“ plus about 1/4” of threading into the case would be 1-1/2“ lengths just to get the shafts flush to the outside cover.
(which won't help you remove them.
So you'd need to cut off about four pieces at least 2” long. 2“ bolts with the heads cut off would also work.

These are app. 3” long sections of all-thread. 16)
Install them into the case, hang the gasket on them and install the cover.
The longer length pieces will allow you to center the cover bushings up to the cams easier for a straight push home. 17)
Once the cover is on, install some 1/4“ mounting bolts and pull the all-thread out.
Then install the remaining bolts and torque to proper specs using a cross pattern. 18)
Push the cover on carefully by hand. Do not use the
screws to pull the cover flush against the case. 19)
1/4”x20 bolt lengths and torque. 20)

Engine Case / Sump Drain Plugs

Sump drain on 04 model 21)

Crank Assembly


The same flywheel set was used in all Sportsters 95-99.
Sold as a unit: part number (23905-89A) consists of the flywheels, shafts and rods.
Each flywheel casting number (23931-88A)
Connecting rod set: part number (24275-86A)
Left connecting rod casting number (24320-83)
Right connecting rod casting number (24321-83)
Rod bearing set (24354-87A)
Rod bearing race - front (2)-(24341-52A)
Rod bearing race - rear (2)-(24352-52A)
Piston pin bushing std (2)-(24331-36), .01“ O.S. (24332-36
Crankpin std (23960-80A), .001” O.S. (23948-87), .002“ O.S. (23949-87)
Crankpin boss washer (2)-(6508)


Flywheel assembly 23905-00 22)
Flywheel assembly 23905-00A 23)


91-99 (all) Flywheels.
Flywheel set part number (23905-89A).
Each flywheel casting number (23931-88A).

91-99 Flywheels 24)
Crank pin boss washer (5608) 25)

From '91 to '03 the Crankshaft/Flywheel was balanced according to the engine size, either for 883 pistons or 1200 pistons. From 2004-later, the flywheels are balanced to be between the weight of the 883 & 1200 pistons. 26) This is one reason why riders would use Wiseco pistons in early (pre-2004) 883 to 1200 conversions - the Wiseco 1200 piston & pin was closer to the weight of the 883 combination rather than the 1200 piston & pin from HD.

Crank Pin

Crank pin (23960-80a) used from L81-03.

L87-03 crank pin 27)

Connecting Rods

Pinion Shaft

Removing / installing the pinion shaft nut

To remove or install the pinion gear nut,
You'll need to lock the pinion gear from moving while turning it.
It's very important to hold the crank on the pinion side with an appropriate pinion locking tool whenever you take the pinion nut off or put it on.
If you hold the crank still from the primary side (or by putting the bike in gear and holding the brake),
The twisting torque applied to the pinion nut gets transmitted through the crank, from one side to the other.
The crank pin is not designed to resist much twisting force.
You'll risk scissoring the crankshaft (knocking the crank out of true), which requires a full tear-down to fix. 28)
So this is one of those situations where it's best to use the proper tool. 29) The pinion nut takes a 15/16” wrench size.

90 and Prior Models (4 Speed)

Homemade Pinion Gear / Removal / Installation Tools 30) Homemade pinion gear press 31) Pinion Gear Puller 32)
Large fender washer cut into a “C” shape and a gear puller
Homemade Pinion Gear Puller 33)
3/8“ stainless steel plate with 20° spokes (for 18 teeth),
sawed initial groove to depth and widened it with files
Homemade pinion gear locking tool for '89 models 34)

91 and Up Models (5 Speed)

See also in the Sportsterpedia:
Oil Pump Drive Gear
Origin of the Grindlock Tool

  • You can use a 15/16” wrench or deep well socket to remove / install the pinion gear nut.
  • The Grindlock Pinion Shaft Locking Tool engages for the full depth of the pinion gear for max. strength.

35) 36)

  • Due to a change in the pinion gear in 2000, there are 2 different versions of this tool:
    (L) - (91-99) year models & (R) - (2000 to present) year models 37) 38)

39) 40) 41)

  • Once the pinion shaft nut is removed, the pinion gear may or may not slide off by itself.
    You can use a gear puller to remove it if it is stuck on.
  • It's very important to hold the crank still from the cam side (not the primary side) when torquing the pinion nut. 42)
    If you for example put the bike in gear and hold the rear brake and torque on the nut, you run the very real risk of knocking the crank out of true.
    It's not designed to transmit torque from one side to the other and it tries to twist the crankpin connection.
  • In respect to the key shearing, it's a very common issue particularly when heavy valve springs are used.
    However, it shouldn't be the one thing that keeps the gear from spinning. The clamp load should do that.
    The caption in the second pic below describes the fix:
    Loctite red and 70ft-lbs instead of the factory specified 50ft-lbs. You won't have this issue again.

43) 44)

Pinion Gear Runout

Attach a scrap piece of metal to the outside of the gearcase and position a gauge holder on it so it won't move while turning over the engine. 45)
Install a dial gauge on the holder with the pointer on
the pinion shaft. Find the lowest spot while turning
the engine over and 'zero' the indicator. 46)
This setup is made with a piece of angle iron for the magnetic base to stand on 47)
This gauge post is threaded into a cover mount hole. 48)

2) , 20) , 35) , 39)
photo by Hippysmack
5) , 7)
photo by goinsideways136 of the XLFORUM http://xlforum.net/forums/showthread.php?t=385092
photos by goinsideways136 of the XLFORUM http://xlforum.net/forums/showthread.php?t=385092
photo by caseyjones, markups by Shu http://xlforum.net/forums/showthread.php?t=922143
13) , 14) , 15) , 16) , 17) , 18) , 24) , 25) , 27)
photos by Hippysmack
Grindlock 91-99 & Grindlock 2000, designed by XLFORUM member, “~Grind~” and Built by Hammer Performance ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=1618841
photos by anachris of the XLFORUM
photo by Grind of the XLFORUM
photos by dezzertrat of the XLFORUM http://xlforum.net/forums/showthread.php?t=1860581
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