Short frame motors are 1957-1966 XL / XLH and 1958-1969 XLC / XLCH.
Long frame motors are 1966-up XLH and 1970-up XLCH.
All sportsters 1957-1966 and 1967-1969 XLCH were virtually identical in design. So most parts thru that period do interchange seamlessly.
The differences that do exist are easy to deal your way around.
The XLForum seems to have adopted the term 'short frame' to describe the 1st generation bikes.
(because their frames were shorter than the 2nd generation “long frame” bikes that came into being to hold all the electric start stuff in 1967)
These motors are also known as “no hump” motors as the left cases were not cast to accept a starter (kick only cases).
1967-1969 XLH was not 1st generation design though many of these second generation parts will retro-fit to the 1st generation design bikes.
Some don't make that an easy task as they are similar but not the same. 1)
1967-up XLH and 1970-up XLCH motors are also known as “hump” motors as the left case is cast with a “hump” over the tranny to mount a starter.
In 1967, to power the starter, a giant battery was required.
To make room for this, the rear frame down tubes were offset to the rear with a “dogleg” and now the frame got longer than the original.
The original is a “short frame” and the doglegged version is a “long frame”.
See the long frame (dogleg) in the pic below. Note the position of the down tubes to the motor mount surface. 2)
Swapping motors and frames:
1952-1976 motors will be a direct bolt-on to 1952-1976 frames (may have to deal with or add bracketry for oil tanks and battery trays depending…)
1977-1985 motors will be a direct bolt-on to 1977-1985 frames (must use the motor mounts that fit the frame year).
All 1957-1966 XL / XLCH and 1967-1969 XLCH motors are basically the same (short frame) and will be a direct swap within those year (kick only) frames.
But the 1967-1969 XLH are different (long frame “hump”) motors. From 1967-1969, there were two sportsters; Short XLCH and Long XLH.
All 1970-up bikes used the long frame.
1967-1976 electric start “hump” engines will bolt directly into the early kick only frames.
What won't bolt on from there is the matching e-start accessories (oil tank or battery box). 3)
The e-starter is well forward of the seat tubes. You may have to do a slight amount of clearancing for the aluminum starter housing.
Or just run kick only and make it real simple.
If swapping early motors into 1977-newer frames, just remember to use the front and rear mounts for the year the frame is. 4)
Short frame motors will bolt into long frames but the dog leg seat posts will show on the later frames. 5)
Swapping case halves:
You can physically bolt any 1952-1976 case halves together (need to remove center dowel pin in certain combos). 6)
That does not mean that the cylinder spigots and crankshaft will exactly line up between the two halves.
Further machining may need to be done to pair the two halves (look for a good machinist if so).
There usually is a slight mismatch at the base surfaces. It's up to each owner if you need to re-skim these.
Keep in mind the factory work is pretty damned good. It's easy to correct the surface mismatch and introduce a parallelism to crankshaft center line error. 7)
In 1952, the K model was introduced. This was a brand new design for HD.
Between 1952 and 1976, that basic bike slowly evolved.
It was built on the same “mechanical DNA” and lots of stuff directly interchanges between a 1952 and 1976.
In 1977, the basic design changed. Fitting a 1977 engine into a 1976 frame requires mods to the frame.
The F model flatheads (side valve in factory speak), from 1952 to 1956, the bike changed each year.
But the changes were evolutionary rather than revolutionary. You could pretty easily put 1956 stuff on your 1952 and vice versa.
In 1957, the OHV XL came along. This new engine was fitted to the same basic frame. It was still the same bike for the most part.
You could put the OHV engine in the flattie frame and vice versa. Same in 1958. Basically one bike so far.
In 1958, the factory took that basic bike and introduced a new model along side the XLH, the XLCH.
The XLCH is the same motor and frame and everything bolted on is just stripped down but still the same bike.
These two models, linked at the hip, were produced until 1966.
1957-1966 (all) and 1957-1969 (XLCH) are kick start only.
Click on a pic to enlarge:
1957-1966 (All) and 1967-1969 (XLCH) (short frame) Cases. Quick glance visuals. 8) | |
In 1967, a mutation in the DNA resulted in the 1st change away from the original design.
Electric start was offered on XLH. A “hump” was added to the left case casting above the tranny.
It was decided to put the electric starting components behind the rear cylinder mounted to the crankcase above the new case “hump”.
New (XLH only) “hump cases” with “long frames” were made to accept the new starter.
The 1967-1969 XLCH was unaffected until it also succumbed in 1970.
1967-1969 (XLH) and 1970-1976 (all) are electric and / or kick start. 9)
You may see many XLHs that added the Option Kicker Kit. 10)
1967 XLH had both Kick and Electric start as the Factory wanted to be “Certain” the Electric proved positive.
In 1968, the Kicker was gone on the XLH, you may see many that added the Optional Kicker Kit (thats how HD makes their money).
On long frames, mechanically speaking, 1967-1969 (XLH) and 1970-1971 (all) cases interchange. 11)
Cosmetically speaking, only 1967-1969 XLH cases are identical.
1967-1969 XLH (long frame) Right Case 14) |
1972-1976 (long frame) cases are machined for 1000cc cylinders.
There was a late 1973 cylinder and head change but the crankcase was left unchanged 15).
All 1000cc cylinders will fit into all 1000cc cases. You just have to use either 72-E73 heads AND cylinders or L73-up heads AND cylinders.
1972 right case has the hole for the speedometer drive gear that runs off the countershaft low gear in the transmission.
1973-up right case does not have this hole and the speedometer drive unit was moved to the front axle. First year for front disc brakes also.
Click on any pic to enlarge.
1973-1976 XLH / XLCH 1000 cases 16) | |
1973-1976 XLCH 1000 cases 17) | |
Cases were redesigned in 1977 to include a mini oil sump and a new gerotor type oil pump mounting boss.
The oil collection sump is in the right case bottom and the left case bottom is sloped to drain into the right case.
A vertical oil scavenge passage is drilled in the right sump wall connecting the crankcase to the oil pump return port.
1977-up frames got a divot on the right side tube to allow removal of the oil pump without removing the engine.
Crankcase breathing was dramatically redesigned. The oil trough between the crankcase and gearcase was deleted.
The crankcase now breathes thru holes drilled in the wall between the crankcase and gearcase and the timed breather was deleted.
This right case has mid 1980 changes to the upper gearcase (mods the factory made to improve sealing between the cover and the case).
Belly number 780 277004 (October 4, 1979).
See Upper Oil Feed Galley below for more information.
The generator was deleted and the machined hole in the right case for the generator was also deleted.
That portion of the case is now designed for a bolt-on oil filter mount.
A stator is now mounted to the trap door. The left case has a channel cast in for the stator wiring leading to a thru hole for a wire grommet.
1957-1969 Sportster Serial# / Vin Pad Location 29) | 1970-E1971 Sportster Serial/VIN Pad Location 30) | L1971-1985 Sportster Serial / VIN Pad Location 31) |
Counting the Ribs:
1957-1971 left cases (above pic) have 4 horizontal ribs under the serial number pad.
1972-1985 left cases have 5 horizontal ribs in that same location (below pic).
An extra rib was added in place of the number pad in 1972 when they stopped casting the number pad on the left case.
Click Here to see the Engine Case Number page in the Sportsterpedia.
Click Here to see an article on Part Numbers in general in the Sportsterpedia.
You will not find any part numbers on the cases that match the parts listings in the parts catalogs.
Part numbers were never cast or stamped into the cases. Each case half has many numbers on it but none of them show up in the parts books.
There were some parts that did have part numbers on them either stamped or on a sticker label.
Some electrical parts had stickers with the part number on them but no part numbers on cases.
The parts catalog listings are for logistics in which the MoCo stocks parts, sells them to dealerships and customers all under one Part Number.
Basically the part number was created to move the product, not to build the product.
Moving the product can mean, to the builders at the factory, mechanics at the dealership or to the customer.
Part numbers are used in manuals and instructions .
Part numbers are assigned after the parts are built (more accurate to be said the part will be listed as XXXX part number when it gets built).
Each case half has a casting number, not to be confused with a part number. See below.
1957-1975 case halves have their own part numbers with the set also having a part number.
That's because you could buy a full case set or you could buy a left or right case half.
1976 and up cases were only sold as a set so there are no individual part numbers for left or right case halves, only a part number for the set.
Click Here to see an article on Casting Numbers in general in the Sportsterpedia.
Casting numbers were created when the mold was created (casting number was “cast” into the part) and will not be stamped into the part. 33)
Casting numbers on the left and right cases look like (are coded like) part numbers but they are not.
They were put there when the case half was created (cast) and represent a certain base design.
Unlike part numbers, casting numbers do pertain to the building of the part. One could also call them design numbers.
A casting part number does not pertain to any certain model.
Many different year / model motors may carry the same casting numbers but there will still be differences that are important to know.
When the main design changed, so did the casting numbers, but not until then. However, the part number may change several times.
Example: 1957-1976 right cases all carried a -57 casting.
Short frame right cases have 3 fittings tapped behind the rear cylinder for oil tank fittings.
However, the E-start year cases (long frame) only have one fitting tapped for the oil return.
These tapped holes are vertically drilled thru to either the oil pump or cam chest.
But the casting part number (24558-57) stays the same even though the machining changed.
Example: 1977-1980 Sportster cases carried the same left casting number (24534-75) and the same right casting number (24558-75).
The main case design was the same but within these years, there were 4 different part number changes.
Different machining (kicker or no, oil galley slot or hole etc) took place that made a new part number.
So even though the main design and casting numbers are the same, there are still different features between them.
These different features may or may not pose a problem when mixing cases or ordering parts and gaskets.
Casting part numbers per years used:
Early model cases did not have any manufacturing date codes.
Else you should find, somewhere on the outside of each case half, a set of numbers representing the day and the year that part was cast.
In the early years, usually there will be 4 numbers (2 for the month followed by 2 for the year, last two digits).
In later years, a slash was added between the month and year. Example: (12 64 is December 1964), (12/75 is December, 1975)
When reading this number code, keep in mind that the months for new models range from late June to early July.
A case that was cast in January of 1964 was most likely made for 1964 models.
A case that was cast in December of 1964 was most likely made for 1965 models.
Looking over many casting date codes and cross referencing that with known VINs can give a clue to how close these events were to each other.
They should be within a month or two apart (the exact day of machining can't be deciphered from these numbers).
The casting date shows what month but not what day and the serial/VIN doesn't have anything to do with dates.
So that process is not very useable on 1957-1974 models without further information.
On 1975-1985 models, matching the date code and crankcase numbers is easier since the crankcase number has the Julian date code system.
That gets you a certain day and month the case was machined then of course the casting date will be a month or two before that.
Belly numbers don't have anything to do with issuing a VIN and they will not tell you specific model info (XLH or XLCH).
Engine serial / VIN numbers are added much later after assembly. 35)
Belly numbers tell you that a particular set of cases was paired up and finish machined together (line boring, cylinder base surfacing etc).
The belly numbers will tell the year model that the cases are intended to be used on.
And also either a sequential number (57-74) or Julian date and sequential number (75-85).
Each case half should have the same exact belly numbers.
L1984-1985 crankcase number locations 39) | Example using Julian Calendars in SP | |
In addition to belly numbers, there is a second set of numbers on 75> motors on each case half that should match.
This was added the same time the left case belly number moved from the belly to the primary wall on 1975 models.
For lack of public documentation, we'll call these Case Match Numbers and they represent the fact that those two case halves were mated as a factory pair.
These will most likely be a letter(s) and numbers but the exact number set should be on the outside of each case half opposite one another.
The factory belly numbers should be the same and the case match numbers should also be the same.
There does not seem to be any connection between the case match numbers and belly numbers (no date coding visible on case match numbers).
These numbers pertain to the whole bike, not just the engine. Coding for these numbers changed over the years.
Click Here to see the VIN page in the Sportsterpedia for specific information on serial/Vin numbers.
An XLCH may have many different parts, over the whole bike, than an XLH, including the engine.
The serial/VIN number was (most likely) the last number to be stamped onto the engine case from the factory.
1957-1969 Sportsters are titled to the engine only so the motor serial number is your proof of ownership of the entire bike.
1970-up Sportsters are titled to the frame only so the motor VIN number has nothing to do with ownership of the bike.
However, having the motor VIN matching the frame VIN is a plus for those who want factory original parts.
And it helps toward the value (or haggle factor) on resell but the VIN is not the only factor in whether you have an original engine or bike.
Click Here for more information on Sportster drain plugs in the Sportsterpedia.
Case drain features from 1957-1985:
Click Here for more information on crankcase oil scavenging paths.
Oil feed comes from the oil pump to the motor thru internal passages in the cam cover.
The gearcase floor has an internal hole from the oil pump inlet to feed into the cam cover bottom.
There is a (relatively) vertical internal feed galley in the cam cover that does not enter the gearcase.
Oil then transfers to the engine in two separate places, a hollowed pinion shaft to crankpin and the top of the gearcase to the rocker box lines.
Click Here to reference the Ironhead Oil Tank, Lines and Routing page in the Sportsterpedia.
Click Here to reference the Ironhead Oil Pump page in the Sportsterpedia.
Note: Mixing full oil pump assemblies and engine cases is much easier than mixing individual oil pump parts.
1957-1976 cases use a gear driven type oil pump.
Any 1957-1976 Sportster oil pump (as an assembly) will bolt up to all 1957-1976 motors but the plumbing has to be taken into account.
1957-1976 oil pumps will not bolt to 1977-up cases.
1977-1985 cases use a gerotor type oil pump.
Any 1977-1985 Sportster oil pump (as an assembly) will bolt to all 1977-1985 cases. 1977-1985 oil pumps will not bolt to 1957-1976 cases.
L1983-1985 gerotors will mount to 1977-E1983 pumps but will destroy them. Click Here for more information on L1983 pump changes.
1957-1971 breather tower bore with machining for oil screen 71) | 1972-E1973 breather tower bore with machining for oil screen 72) | L1973-1976 breather tower bore has no machining for oil screen 73) |
Click Here for more information on crankcase oil scavenging paths.
Click Here for more information on crankcase ventilation.
1957-1976 Sportster right case bushing (24585-57) is held in place by way of set screw pins.
Sportster Pinion Shaft Bearing Bushing Screw Part# (24608-54) x 2.
1977-up Sportster right cases do not use this bushing or screws.
The transmission countershaft boss changed over the years for strengthening issues.
The 52-53 is the 1st iteration of the design. Each after that is noted as to the upgrade.
Starting L1966 with engine number (66XLCH 6117) on 1-13-1966, a fillet was added at the base of the countershaft low gear boss.
Also, new countershaft low gear has a counterbore to provide clearance at this point.
The old countershaft low gear can not be used on crankcases having the fillet on the countershaft bushing boss because it will jam against the fillet. 87)
Here is a cross section view of the right case at the countershaft boss.
88)
1957-1976 models vent the primary / transmission thru the motor internally via the oil transfer valve so there is no external vent.
Click here to read more on the transfer valve in the Sportsterpedia.
1977-1985 models vent to atmosphere out the back of the motor from the top of the transmission near the rear motor mount just behind the solenoid.
Click here for more information on the trans/primary vent in the Sportsterpedia.
Click Here to view the Ironhead Motor Mount page in the Sportsterpedia.
Always use the style front mounts that match the frame year intended.