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| techtalk:evo:transfinal01 [2025/08/13 08:05] – [Final Drive Sprocket - Stripped Splines] hippysmack | techtalk:evo:transfinal01 [2025/08/14 05:06] (current) – [Final Drive Sprocket - Stripped Splines] hippysmack |
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| ====== Final Drive Sprocket - Stripped Splines ====== | ====== Final Drive Sprocket - Stripped Splines ====== |
| **Symptoms**: \\ Symptoms of stripped splines include feeling like the clutch or transmission is "slipping" or "jumping" out of gear. It may appear as slipping or lurching from a certain gear and later progress as slipping in all gears depending on the amount of spline damage. Generally it has been described by many as a "lurching" in 1st and maybe even 2nd to begin with under light to medium acceleration (lower gears are usually under more torque than higher gears). And it will most likely progress to happen in higher gears under power. Careful shifting may make it seem less of a problem. \\ | **Symptoms**: \\ Symptoms of stripped splines include feeling like the clutch or transmission is "slipping" or "jumping" out of gear. It may appear as slipping or lurching from a certain gear and later progress as slipping in all gears depending on the amount of spline damage. It seems some people have different experiences, as shown below. |
| | * *Lurching" in 1st and maybe even 2nd to begin with under light to medium acceleration (lower gears are usually under more torque than higher gears). And it will most likely progress to happen in higher gears under power. Careful shifting may make it seem less of a problem (splines still present with light to moderate damage). |
| | * Under slow acceleration, the nut may hold it with no lurching/slipping. But when you get on it, it may slip and jump and chatter (splines still present with light to moderate damage). \\ |
| | * Bike won't move with motor running and transmission in any gear (splines fully stripped out). |
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| **Causes**: \\ | **Causes of Stripped Splines**: \\ |
| This problem is usually caused by the lock screws and the main nut becoming loose. With even a little play, the pulley will rock on the shaft every time you open or close the throttle. This will cause wear on the splines no matter what material the pulley is made of. ((steelworker of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/163019-drive-pulley-number-2)) The stock pulley is made of softer metal than the transmission mainshaft and the pulley will generally wear out before the mainshaft. Although the splines on the mainshaft should be inspected as well as they may get some wear from the pulley rocking back and forth (which has also been a problem to some). It doesn't happen every time but it can and has happened before. So you may notice seemingly good mainshaft splines when you remove the offending pulley. But if you install a new pulley with good splines and still notice a little slop between the pulley and mainshaft, replacing the mainshaft as well may help. ((biknut of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/93208-bike-crapped-out-may-need-help-from-you-guys/page3)) \\ | This problem is usually caused by the lock screws and the main nut becoming loose. With even a little play, the pulley will rock on the shaft every time you open or close the throttle. This will cause wear on the splines no matter what material the pulley is made of. ((steelworker of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/163019-drive-pulley-number-2)) The stock pulley is made of softer metal than the transmission mainshaft gear and the pulley will generally wear out first. Although the splines on the mainshaft gear should be inspected as well as they may get some wear from the pulley rocking back and forth (which has also been a problem to some). It doesn't happen every time but it can and has happened before. So you may notice seemingly good mainshaft splines when you remove the offending pulley. But if you install a new pulley with good splines and still notice a little slop between the pulley and mainshaft, replacing the mainshaft as well may help. ((biknut of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/93208-bike-crapped-out-may-need-help-from-you-guys/page3)) \\ |
| | * Pulley nut wasn't properly torque'd (including Loctite) upon last installation. \\ The nut holds clamp force against the drive gear shaft. \\ It doesn't have to look loose to not have enough clamp force to hold it tight when pressure from the transmission comes onto the pulley. |
| | * Retainer plate screws loose/missing and allowing the pulley nut to loosen. |
| | * Worn splines on mainshaft (harder metal). |
| | * Worn splines on drive pulley (softer metal). |
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| | **Causes Other Than Stripped Splines**: \\ |
| | Keep in mind that these symptoms do not just have to be associated with stripped splines. \\ |
| | There are other issues that may exhibit the same symptoms. \\ |
| | If you suspect the splines have stripped or are on their way out, move to Diagnosing below. \\ |
| | * Damaged transmission gear dogs has about the same symptoms (except for jumping/lurching in all gears). |
| | * Some of these symptoms are also noticed with clutch problems. |
| | * A drive belt that is too loose may skip a tooth on the drive pulley especially at low speed and 1st gear. |
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| **Diagnosing**: \\ | **Diagnosing**: \\ |
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| **Removal**: \\ (Caution: LEFT HAND THREADS ON SPROCKET NUT = CLOCKWISE TO REMOVE) \\ | **Removal**: \\ (Caution: 1991-UP MODELS HAVE LEFT HAND THREADS ON SPROCKET NUT = CLOCKWISE TO REMOVE) \\ |
| The 2 cap screws are right hand thread. Remove them and the metal retaining plate first. Then remove the pully nut. You'll most likely need a breaker bar also if not using an impact wrench to remove the 1-7/8" nut (it takes a lot of torque to break it loose). And you'll need to either lock the transmission from turning or lock the pully from turning to use a breaker bar/socket to remove it. \\ | The 2 cap screws are right hand thread. Remove them and the metal retaining plate first. Then remove the pully nut. You'll most likely need a breaker bar also if not using an impact wrench to remove the 1-7/8" nut (it takes a lot of torque to break it loose). And you'll need to either lock the transmission from turning or lock the pully from turning to use a breaker bar/socket to remove it. \\ |
| * [[techtalk:ref:tools131|Click Here]] to view sprocket tools in the Sportsterpedia. | * [[techtalk:ref:tools131|Click Here]] to view sprocket tools in the Sportsterpedia. |
