EVO: Engine Mechanicals

Timing Inspection Hole


Motor Mounts

Click here for Engine Mounts in the Evo Suspension section of the Sportsterpedia.

Cylinder Mounting Studs

Weakest cylinder mounting stud holes in the case. 1)

Cam / Gearcase Cover

Sub Documents

#2 Cam - Cover Seal (86-03)

Seal number (11124):
This surrounds and seals #2 cam when the cover is installed.
See also Removal / Installation of the #2 cam cover seal in the Sportsterpedia.

This side faces out. 2) This side faces #2 cam shaft. 3)

Primary Cover


Shifter shaft Seal

Navigate to the appropriate year model transmission pages in the Sportsterpedia for removal/installation.
Part numbers:
2003 and earlier (37101-84)
2004-2005 (37101-84A)
2006-up (37107-06)
There is a steel bushing pressed into the bore in the cover. The seal installs on the outside of the bushing with a light press fit.
The seal can be removed/installed without removing the primary cover.

Shifter shaft seal on 1998 1200S primary cover.
4) 5)

Shifter shaft seal on 2006 1200R primary cover.
6) 7) 8)

Primary Inspection Cover

Engine Case / Sump Drain Plugs

Sump drain on 04 model 9)

Flywheel Assembly

Year Model 10)Flywheel
Connecting Rod
Early 1986 Models
E1986 XLH88323905-8624275-8623960-80A
E1986 XLH110023900-8624275-8623960-80A
Late 1986-1990 Models
L1986 XLH88323905-86A24275-86A23960-80A
1987 XLH88323905-8724275-86A23960-80A (std)
23948-87 (.001“ O.S.)
23949-87 (.002” O.S.)
1988 XLH88323905-88
1989-1990 XLH88323905-88A
L1986 XLH110023900-86A24275-86A23960-80A (std)
23948-87 (.001“ O.S.)
23949-87 (.002” O.S.)
1987 XLH110023900-87
1988 XLH120023900-8824275-86A23960-80A (std)
23948-87 (.001“ O.S.)
23949-87 (.002” O.S.)
1989-1990 XLH120023900-88A
1991-1999 Models
1991-1994 XLH88323905-8924275-86A23960-80A (std)
23948-87 (.001“ O.S.)
23949-87 (.002” O.S.)
1991-1994 XLH120023900-9024275-86A23960-80A (std)
23948-87 (.001“ O.S.)
23949-87 (.002” O.S.)
1995-1999 All Models23905-89A24275-86A23960-80A (std)
23948-87 (.001“ O.S.)
23949-87 (.002” O.S.)
2000-2003 Models
2000-2003 All Models23905-00
Not Sold
Not Sold
2004-up Models
2004-2005 All Models23905-04Not Sold
Not Sold
2006-2009 All Models
(Except XR1200)
23905-04ANot Sold
Not Sold
2010-2019 All Models
(Except XR1200/X)
23905-04BNot Sold
Not Sold
XR1200 / XR1200X
23999-08Not Sold
Not Sold


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)
Front connecting rod casting number (24321-83)
Rear connecting rod casting number (24320-83)
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)


The OEM Flywheel assembly (23905-00) was factory installed in all Sportsters 2000-2003.
That's to say the entire assembly part number is the same from 00-03.
However, the rods in the 2000-2002 assemblies are reportedly thicker than the 2003 assembly. 11)

The entire assembly was sold as a unit with no published part numbers for it's individual parts.
To date, we have no pics or casting numbers on the 00-02 rods for comparison.
Rod bearings and races, crankpin and even the shaft nuts were not mentioned in the parts catalogs.

Piston Pin bushing, standard (24331-36), 0.01” O.S (24332-36)
Inner bearing ring (24658-87)
Retaining ring (11177A)

Flywheel assembly 23905-00 12) Flywheel assembly 23905-00A 13)


The original OEM Flywheel assembly (23905-00) was factory installed in all Sportsters 2000-2003.
However, the rods in the 2003 assemblies are reportedly thinner than in the 00-02 assembly and carry -02 casting numbers. 14)
So the original 2003 flywheel version appears to be a one year only version.

Entire assembly was sold as a unit with no published part numbers for individual parts for the assembly.
Rod bearings and races, crankpin and shaft nuts were not mentioned in the parts catalogs.

  • The assembly in the pics below came from a 2003 883R:
    • Front connecting rod casting number (24225-02)
    • Rear connecting rod casting number (24224-02)

Piston Pin bushing, standard (24331-36), 0.01“ O.S (24332-36)
Inner bearing ring (24658-87)
Retaining ring (11177A)

Flywheel assembly 23905-00 15)
Flywheel assembly 23905-00 16)


Late 1986 flywheels and crankpin bearing changes.
Information from Technical Service Bulletin #M-927. Click here to see the actual bulletin from this page in the Sportsterpedia.
Beginning with crankcase numbers 883cc (1786 083 003) and 1100cc (1886 090 012), a new (F.A.G.) crank pin bearing set and revised flywheels were installed at the factory.
The new crank pin bearing set (using the existing crankpin P/N) consists of three bearings in a package. Early production engines were assembled without thrust washers.
L1986-later production flywheels had thrust washers staked into a counter-bore in the flywheels. The L86 crank pin bearing set retrofits earlier models.
However, the new bearings require a stepped flywheel thrust washer to provide clearance for the wider bearing cages.
You will select the correct thrust washer for your particular assembly and machine off the raised lip in the area of the flywheel thrust washers' I.D.
This lip must be machined off or you will crush the bearing cage as you assemble and torque the crankpin nuts.
See Tech Tip #14, Instruction Sheet #J00022 and Instruction Sheet #J00025 in the Sportsterpedia for more information.

The L86 XLH883 flywheel assembly is (23905-86A) and the L86 XLH1100 flywheel assembly is (23900-86A).
There were new crank pin bearing clearances also.
The new crank pin bearing set packages were color coded with either a red or a blue identification. This color coding is used by the bearing manufacturer only.
The color coding DOES NOT indicate size selection for crank pin bearing replacement.

1989 flywheel changes.
Information from Technical Service Bulletin #M-971. Click here to see the actual bulletin from this page in the Sportsterpedia.
Beginning June 1, 1988, flywheels forged from a micro-alloyed steel went into production. Part numbers and color codes of assemblies with the new material were changed.

1991-1994 Flywheels.
From '91 to '94 the Crankshaft/Flywheel was balanced according to the engine size, either for 883 pistons or 1200 pistons. From 1995-later, the flywheels are balanced to be between the weight of the 883 & 1200 pistons. 17) 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 stock 1200 piston & pin from HD.

1995-1999 Flywheels.
Flywheel assembly part number (23905-89A).
Each flywheel casting number (23931-88A).

2000 Flywheels:
There are no timing marks on the wheels for any of the rubber mounts. 18)
Nor is there a timing window (on the case) to look through to see the mark that's not there.
And for that matter, there's no way to change the timing, even if you had a window to see the mark that's not there.
The only way to change the timing on a rubber mount is to use an aftermarket ignition that gives you control, through dials and/or a programming kit.
And even doing that, there's no way to measure it, you just have to trust that it's delivering the timing you're telling it to.

95-99 Flywheels 19)
L1986-up crank pin boss washer (6508) 20)

Crank Pin

Crank pin (23960-80A) used from L1981-2003.

L87-03 crank pin 21)

The sprocket shaft nut torque for 2004 & later Sportsters and 2003 & later Buell XB models has been changed. 22)
The torque has been increased from 190-210 ft-lbs. to 240-260ft-lbs.
Remember to clean the threads and generously apply LOCTITE Threadlocker 262 (red) onto the threads of engine sprocket shaft and use a sprocket locking tool.
Some examples of sprocket locking tools are here in the tools section of the Sportsterpedia.

Connecting Rods

Rod set (24275-86A) includes bearings, crankpin and nuts.
Below are pics of just the rods off a 1998 1200S model.
The part numbers cast into the rods are front (24321-83) and rear (24320-83).

Below is the rod set known to be fitted to at least 2003 model Sportsters.
Front casting number (24225-02)
Rear casting number (24224-02)

23) 24) 25)

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. 26)
So this is one of those situations where it's best to use the proper tool. 27) The pinion nut takes a 15/16” wrench size.

90 and Prior Models (4 Speed)

Homemade Pinion Gear / Removal / Installation Tools 28) Homemade pinion gear press 29) Pinion Gear Puller 30)
Large fender washer cut into a “C” shape and a gear puller
Homemade Pinion Gear Puller 31)
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 32)

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” 6 point 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.

33) 34)

  • 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 35) 36)

37) 38) 39)

  • 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. 40)
    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.

41) 42) 43)

Pinion Shaft Runout

Check to see if your crank is out of true. See Measuring Pinion Shaft Runout in the REF section of the Sportsterpedia.

Crankshaft Seal

Here is a trick to hold the spring in place to stop it popping off while you are fitting the seal. 44)
Before fitting it, pack some grease around the spring in the seal groove. You only need a small amount.

Crankshaft Seal (35151-74A) 45)

1) , 2) , 3) , 4) , 5) , 33) , 37)
photo by Hippysmack
6) , 7) , 8)
photo by hdmc_ru2 of the XLFORUM, labeled by Hippysmack http://xlforum.net/forums/showthread.php?t=49915&page=7
1986-2019 HD Sportster Parts Catalogs
19) , 20) , 21)
photos by Hippysmack
HD Tech Tip #211 dated September 16,2005
23) , 24) , 25)
Pics courtesy of Ebay seller, house of parts 815. Link to Ebay Store
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
photo by npaisnel of the XLFORUM, labeled by Hippysmack http://xlforum.net/forums/showthread.php?t=2077485&page=26
photos by pearlmoto of the XLFORUM http://xlforum.net/forums/showthread.php?t=1815630
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